商务统计学 Statistics for Business

What is the purpose of this course? To introduce you to the basic concepts of descriptive statistics found in business To introduce you to the basic concepts of descriptive statistics found in business To give you basic knowledge and skills required to use basic statistical and graphical techniques to address business problems To give you basic knowledge and skills required to use basic statistical and graphical techniques to address business problems

Outcomes of this Course Outcome 1 – Demonstrate an understanding of statistical techniques for collecting data Outcome 1 – Demonstrate an understanding of statistical techniques for collecting data Outcome 2 – Use statistical techniques to analyze and interpret data Outcome 2 – Use statistical techniques to analyze and interpret data Outcome 3 – Produce forecasts based on formalized procedures Outcome 3 – Produce forecasts based on formalized procedures

Assessment There will be 2 assessments to test your knowledge of the subject matter There will be 2 assessments to test your knowledge of the subject matter The first assessment will be a closed- book test covering Outcome one and parts of Outcomes 2 and 3 that is to be completed within 1 hour The first assessment will be a closed- book test covering Outcome one and parts of Outcomes 2 and 3 that is to be completed within 1 hour The second assessment will be an open-book test under controlled conditions using appropriate software and covering the remaining aspects to be completed within 1.5 hours The second assessment will be an open-book test under controlled conditions using appropriate software and covering the remaining aspects to be completed within 1.5 hours

Introduction What is statistics? What is statistics? a discipline which is concerned with: a discipline which is concerned with: designing experiments and other data collection, designing experiments and other data collection, summarizing information to aid understanding, summarizing information to aid understanding, drawing conclusions from data, and drawing conclusions from data, and estimating the present or predicting the future. estimating the present or predicting the future.

Statistics JanFeb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Monthly Average Temperatures in Beijing

Statistics in Everyday Life Even though you may not have realized it, you probably have made some statistical statements in your everyday conversation or thinking. Even though you may not have realized it, you probably have made some statistical statements in your everyday conversation or thinking. Statements like "I sleep for about eight hours per night on average" and "You are more likely to pass the exam if you start preparing earlier" are actually statistical in nature. Statements like "I sleep for about eight hours per night on average" and "You are more likely to pass the exam if you start preparing earlier" are actually statistical in nature.

How did Statistics Begin? Statistics was originally studied by politicians and rulers Statistics was originally studied by politicians and rulers They needed to know information about populations for tax purposes They needed to know information about populations for tax purposes

Other Early Statisticians Florence Nightingale ( 弗洛伦斯 · 南 丁格尔 ) Florence Nightingale ( 弗洛伦斯 · 南 丁格尔 ) Famous English nurse who worked on soldiers during the Crimean War Famous English nurse who worked on soldiers during the Crimean War Studied the statistics of death rates in British hospitals Studied the statistics of death rates in British hospitals Used these studies to improve conditions and reduce death rates Used these studies to improve conditions and reduce death rates

How does Statistics apply to Business? Business And Industry: Statisticians quantify unknowns in order to optimize resources. They: Business And Industry: Statisticians quantify unknowns in order to optimize resources. They: Predict the demand for products and services Predict the demand for products and services Check the quality of items manufactured in a facility Check the quality of items manufactured in a facility Manage investment portfolios Manage investment portfolios Forecast how much risk activities entail, and calculate fair and competitive insurance rates Forecast how much risk activities entail, and calculate fair and competitive insurance rates

The Language of Statistics Statistics is the study and analysis of numerical data Statistics is the study and analysis of numerical data We often use raw information (original data) We often use raw information (original data) Data is often used in terms of: Data is often used in terms of: Data types （资料类型） Data types （资料类型） Data sources （资料根源） Data sources （资料根源） Data collection （资料收集） Data collection （资料收集） Sampling methods （取样方式） Sampling methods （取样方式）

Data Types （资料类型） Qualitative Data （定性资料） Qualitative Data （定性资料） Descriptive Data Descriptive Data Can be described using words, not numbers Can be described using words, not numbers Examples: Examples: Hair color – black, brown, blonde Hair color – black, brown, blonde Marital Status – married, single, widowed Marital Status – married, single, widowed Ethnicity – Han, Mongol, Hui, American Ethnicity – Han, Mongol, Hui, American Often called attribute data or descriptive data Often called attribute data or descriptive data Only allows for very simple statistical analysis in the form of simple graphs and charts Only allows for very simple statistical analysis in the form of simple graphs and charts

Qualitative Data

Data Types （资料类型） Ordinal Data （顺序的资料） Ordinal Data （顺序的资料） Data arranged by rankings or in order Data arranged by rankings or in order First, Second, Third … First, Second, Third … Often used in questionnaires Often used in questionnaires EX: EX: Rate your health on a scale of Rate your health on a scale of 1 (Poor) 2 (OK) 3 (Good) 4 (Great) *The numbers here are only for order, this is not the same as quantitative data

Data Types （资料类型） Quantitative Data （数量资料） Quantitative Data （数量资料） Most beneficial for meaningful analysis Most beneficial for meaningful analysis Numerical Quantities Numerical Quantities Split into two types: Split into two types: Discrete （离散） Discrete （离散） Continuous （连续） Continuous （连续）

Quantitative Data Discrete Discrete Can only take on specific values Can only take on specific values Number of students Number of students Shoe size Shoe size Number of correct answers on a test Number of correct answers on a test Usually only measured in integers （整数） Usually only measured in integers （整数） Countable Countable

Quantitative Data Continuous Continuous Numerical, but cannot assume exact values Numerical, but cannot assume exact values Usually anything that is measurable Usually anything that is measurable Height of children in a class Height of children in a class Weight of members of a health club Weight of members of a health club Temperatures at a resort Temperatures at a resort Measurements can take on any value on a continuous scale Measurements can take on any value on a continuous scale

Sources for Data Collection There are two methods for data collection There are two methods for data collection Primary Data Primary Data Secondary Data Secondary Data

Sources for Data Collection Primary Data Primary Data This is data that is collected first- hand This is data that is collected first- hand It is collected for a specific, predetermined purpose It is collected for a specific, predetermined purpose It is the most effective type of data It is the most effective type of data Expensive and time consuming Expensive and time consuming

Sources for Data Collection Secondary Data Secondary Data Data from other sources (second- hand) Data from other sources (second- hand) May not be specific or relevant May not be specific or relevant May have gaps in information May have gaps in information Inexpensive Inexpensive Can be gathered from books, journals, the internet, etc. Can be gathered from books, journals, the internet, etc.

Data Collection Direct Observation Direct Observation Interviews Interviews Telephone Telephone Personal Personal Respondent’s Schedules Respondent’s Schedules Postal Questionnaires Postal Questionnaires

Direct Observation Watching and Making Notes Watching and Making Notes Examples Examples Number of customers who buy a certain product over a certain period of time Number of customers who buy a certain product over a certain period of time How many people choose a certain meal at a restaurant How many people choose a certain meal at a restaurant Useful for preparing budgets, inventories, etc. Useful for preparing budgets, inventories, etc.

Interviews Interviewers must be well- trained to ensure that the correct information is gathered Interviewers must be well- trained to ensure that the correct information is gathered Questions must be well- constructed to avoid bias Questions must be well- constructed to avoid bias Two methods: Two methods: Telephone Telephone Personal Personal

Interviews Telephone Telephone Enable coverage over a wide geographical area with minimum expense Enable coverage over a wide geographical area with minimum expense Allows for target audience to be as large as necessary Allows for target audience to be as large as necessary

Interviews Personal Interviews Personal Interviews Time Consuming Time Consuming Intimate Intimate Delicate or personal questions can be asked Delicate or personal questions can be asked Requires interviewer to be skilled Requires interviewer to be skilled

Respondent’s Schedules Feedback from sample group over a prolonged period of time on specific items detailed by the researcher Feedback from sample group over a prolonged period of time on specific items detailed by the researcher Often in the form of a diary kept over a specific period of time Often in the form of a diary kept over a specific period of time Food eaten Food eaten Money spent Money spent Television programs watched Television programs watched

Postal Questionnaires Mailed to random respondents Mailed to random respondents Can cover a wide geographical area Can cover a wide geographical area Covers the largest number of people at the lowest possible cost Covers the largest number of people at the lowest possible cost

Postal Questionnaires Problems Problems Return Rate Return Rate Most people will not respond to these types of questionnaires; they will simply throw them away; usually requires a reward for completing and returning the questionnaire Most people will not respond to these types of questionnaires; they will simply throw them away; usually requires a reward for completing and returning the questionnaire

Postal Questionnaires Problems (cont.) Problems (cont.) Design of Questionnaire Design of Questionnaire May have ambiguities ( 含糊 ) May have ambiguities ( 含糊 ) May have leading questions ( 对答案有诱 导性的提问 ) May have leading questions ( 对答案有诱 导性的提问 ) These problems can invalidate ( 使无效 ) the data These problems can invalidate ( 使无效 ) the data

Tips for Designing a Questionnaire Keep the number of questions to a minimum Keep the number of questions to a minimum Keep questions simple (Yes/No questions are best) Keep questions simple (Yes/No questions are best) Avoid leading questions, personal questions and ambiguity Avoid leading questions, personal questions and ambiguity Ensure you have covered every possible response (May include “I don’t know”) Ensure you have covered every possible response (May include “I don’t know”) Don’t use words that produce emotions (May produce biased responses) Don’t use words that produce emotions (May produce biased responses) Test on pilot group before using Test on pilot group before using

Postal Questionnaires Problems (cont.) Problems (cont.) Quality of responses Quality of responses If there is any doubt of the quality of responses, the analysis will be useless If there is any doubt of the quality of responses, the analysis will be useless Postal questionnaires always give an opportunity for dishonest or exaggerated answers Postal questionnaires always give an opportunity for dishonest or exaggerated answers Some questions may not be answered at all Some questions may not be answered at all

Activity (p. 27) Draw a table like the one below Method of collection AdvantagesDisadvantages Observation Personal Interview Telephone Interview Respondent’s Schedules Postal Questionnaires In groups of 3, make a list of the advantages and disadvantages of the different methods of data collection we have discussed

Activity (p. 28) An employer intends to provide a gym for full-time and part-time staff. Prior to setting up these facilities, research is required on demand, types of equipment, whether staff would be willing to contribute to upkeep, opening hours and so on. An employer intends to provide a gym for full-time and part-time staff. Prior to setting up these facilities, research is required on demand, types of equipment, whether staff would be willing to contribute to upkeep, opening hours and so on. In groups of three, design a questionnaire to cover the issues that you think need to be addressed. In groups of three, design a questionnaire to cover the issues that you think need to be addressed. Give the questionnaire to another group of three as a pilot. Give the questionnaire to another group of three as a pilot.

Sampling Methods Statistics is concerned with the analysis of numerical data Statistics is concerned with the analysis of numerical data We must first collect data We must first collect data We have discussed the types of data and methods of collecting data We have discussed the types of data and methods of collecting data Make sure you are familiar with these types and methods Make sure you are familiar with these types and methods

Sampling Methods Population ( 总体 ) - The set of individuals, items, or data from which a statistical sample is taken Population ( 总体 ) - The set of individuals, items, or data from which a statistical sample is taken When observing a population, we are carrying out a census (the official count of a complete group) When observing a population, we are carrying out a census (the official count of a complete group)

Sampling Methods The terms “population” and “census” are usually heard when referring to people. The terms “population” and “census” are usually heard when referring to people. A population census ( 人口普查 ) is an official count of all of the people in a given area A population census ( 人口普查 ) is an official count of all of the people in a given area Observing the entire population is a large task that can take a long time Observing the entire population is a large task that can take a long time

Sampling Methods Instead of using the entire population, which is time consuming and expensive, we can use a representative sample ( 代表性样品 ) Instead of using the entire population, which is time consuming and expensive, we can use a representative sample ( 代表性样品 ) This reduces the amount of work and is easier to manage This reduces the amount of work and is easier to manage Can still give useful and reliable information Can still give useful and reliable information

Sampling Methods Sample Population

Sampling Methods The sample must display all the characteristics of the population The sample must display all the characteristics of the population Any conclusions from the sample can be easily transferred to the whole population Any conclusions from the sample can be easily transferred to the whole population If the sample is not an accurate representative of the population, any further analysis of the data is invalid If the sample is not an accurate representative of the population, any further analysis of the data is invalid

Sampling Methods We will discuss 6 methods of sample selection We will discuss 6 methods of sample selection Random Random Stratified Stratified Systematic Systematic Multistage Multistage Quota Quota Cluster Cluster

Sampling Methods Random Random Stratified Stratified Systematic Systematic Used when we have a database of information. This database is called the sampling frame

Random Sampling Choosing samples without any order to the selection Choosing samples without any order to the selection EX. Drawing numbers out of a hat EX. Drawing numbers out of a hat This method often uses statistical tables or the random number generator on a calculator This method often uses statistical tables or the random number generator on a calculator

Random Sampling Go to Excel File

Stratified Sampling Used for samples from a population that is split into groups Used for samples from a population that is split into groups Sample must reflect the proportions in the population Sample must reflect the proportions in the population Provides greater precision than random sampling Provides greater precision than random sampling

Stratified Sampling MaleFull-time90 MalePart-time18 FemaleFull-time9 FemalePart-time63 Below is the population of a company divided into several strata (groups) Take a sample of 40 staff, stratified according to the given categories

Stratified Sampling MaleFull-time90 MalePart-time18 FemaleFull-time9 FemalePart-time63 Total 180 % Male, Full-time = % Male, Part-time = % Female, Full-time = % Female, Part-time =

Stratified Sampling % Male, Full-time = % Male, Part-time = % Female, Full-time = % Female, Part-time = Male, Full-time = 50% of 40 = 20 Male, Part-time = 10% of 40 = 4 Female, Full-time = 5% of 40 = 2 Female, Part-time = 35% of 40 = 14 For a sample of 40, we should have:

Systematic Sampling Random sampling with a system Random sampling with a system Used when selecting from a population with no pattern or strata Used when selecting from a population with no pattern or strata Choose a random starting point and then select at regular intervals Choose a random starting point and then select at regular intervals

Systematic Sampling EX EX Take a sample of 8 houses from a population of 120 houses on a street Take a sample of 8 houses from a population of 120 houses on a street 120/8 = 15 houses 120/8 = 15 houses We will select every 15th house We will select every 15th house First we must chose a random starting point between 1 and 15 First we must chose a random starting point between 1 and 15 If the random starting point is 11, then the houses selected are 11, 26, 41, 56, 71, 86, 101, and 116 If the random starting point is 11, then the houses selected are 11, 26, 41, 56, 71, 86, 101, and 116

Multistage Sampling The sample is from a large population and must be selected in several stages The sample is from a large population and must be selected in several stages EX EX Choose a sample of primary school students in China Choose a sample of primary school students in China 1st – Randomly choose cities in China 1st – Randomly choose cities in China 2nd – Within those cities, randomly choose primary schools 2nd – Within those cities, randomly choose primary schools 3rd – Within those schools, randomly choose students 3rd – Within those schools, randomly choose students

Quota Sampling Most common in public opinion polls Most common in public opinion polls The interviewer is given criteria for a specific group of people. The interviewer is given criteria for a specific group of people. EX EX A survey for food preferences of children A survey for food preferences of children The interviewer is told to interview 30 boys between 7 and 12, and 35 girls between 8 and 13 The interviewer is told to interview 30 boys between 7 and 12, and 35 girls between 8 and 13 Not completely random, but easy and effective Not completely random, but easy and effective

Cluster Sampling This is similar to random sampling, but instead of choosing random individuals from a population, you choose random clusters from the population and examine every individual within the cluster This is similar to random sampling, but instead of choosing random individuals from a population, you choose random clusters from the population and examine every individual within the cluster

Cluster Sampling EX EX You want to take a sample of 10% of all of the students in a university You want to take a sample of 10% of all of the students in a university Choosing 10% of the students in every class would be too time consuming Choosing 10% of the students in every class would be too time consuming You choose 10% of the classes and interview every student in the class You choose 10% of the classes and interview every student in the class

Cluster Sampling This method is often used by geographers and biologists for examining plant species, bacteria growth, insect population, etc. This method is often used by geographers and biologists for examining plant species, bacteria growth, insect population, etc. While these units may not represent the diversity of the entire population, in certain cases, this type of sampling can be appropriate and effective While these units may not represent the diversity of the entire population, in certain cases, this type of sampling can be appropriate and effective