Presentation on theme: "Group the following as either discrete or continuous data."— Presentation transcript:
1 Group the following as either discrete or continuous data. Volume of a cereal boxPopulation of a townNumber of goals in a seasonNumber of matches in a boxLength of a crocodileShirt collar sizeSpeed of a carTemperature of ovenDiscrete? Continuous?Group the following as either discrete or continuous data.
2 Discrete Continuous Population of a town Volume of a cereal box Number of matches in a boxTop speed of a carLength of a crocodileShirt collar sizeNumber of goals in a seasonTemperature of oven
3 Date: 04/06/2013 Title: Recording data in tables Learning objectives: To be able to design frequency tables for discrete raw data; and design data collection tables for gathering large discrete and continuous sets of raw data, choosing suitable class intervals.
4 Discrete and continuous data Numerical data can be discrete or continuous.Discrete data can only take certain values.For example,shoe sizes,the number of children in a class,the number of sweets in a packet.Continuous data comes from measuring and can take any value within a given range.Ask pupils to give further examples.For example,the weight of a banana,the time it takes for pupils to get to school,the height of 13 year-olds.
5 Designing a data collection sheet A data collection sheet can be used to record data that comes from counting, observing or measuring.It can also be used to record responses to specific questions.For example, to investigate a claim that the amount of TV watched has an impact on weight we can use the following:agesexheight (cm)weight (kg)hours of TV watched per weekPoint out that the headings used in the sheet should incluse units where appropriate.
6 Using a tally chartWhen collecting data that involves counting something we often use a tally chart.For example, this tally chart can be used to record peoples’ favourite snacks.favourite snacktallyfrequencycrispsfruitnutssweets13638The tally marks are recorded, as responses are collected,and the frequencies are then filled in.
7 What is the best size for the class intervals for the race times data? Grouping dataA list of results is called a data set.It is often easier to analyze a large data set if we put the data into groups. These are called class intervals.A frequency diagram or histogram can then be drawn.You will need to decide on the size of the class interval so that there are roughly between 5 and 10 class intervals.On the next page the results are shown again to aid discussion.Ask pupils what the shortest and fastest times are.It is appropriate for the interval to be a multiple of 5 or 10 if possible. The best interval here would be 5 seconds.What is the best size for the class intervals for the race times data?
8 Grouping discrete data A group of 20 people were ask how much change they were carrying in their wallets. These were their responses:34p£1.7283p£6.36£4.07£2.97£3.536p£9.54£1.6850p82p£7.54£1.09£2.81£2.4346p£1.70£1.29Each amount of money is different and the values cover a large range.This type of data is usually grouped into equal class intervals.
9 Choosing appropriate class intervals When choosing class intervals it is important that they include every value without overlapping and are of equal size.For the following data:34p£1.7283p£6.36£4.07£2.97£3.536p£3.54£1.6850p82p£7.54£1.09£2.81£2.4346p£1.70£1.29We can use class sizes of £1:£ £1.00,£ £2.00,£ £3.00,£ £4.00,£ £5.00,Over £5.This is an open class interval.
10 Choosing appropriate class intervals The size of the class intervals depends on the range of the data and the number of intervals required.For the following data:34p£1.7283p£6.36£4.07£2.97£3.536p£3.54£1.6850p82p£7.54£1.09£2.81£2.4346p£1.70£1.29Explain why class sizes of £5 would be inappropriate.Tell pupils that we should aim to have between five and ten class intervals, depending on the data.Could we use a class size of 20p?
11 Grouping continuous data Continuous data is usually grouped into equal class intervals.What is wrong with the class intervals in this grouped frequency table showing lengths?30 ≤ length20 ≤ length < 3010 ≤ length < 200 ≤ length < 10FrequencyLength (cm)30 ≤ length20 ≤ length ≤ 3010 ≤ length ≤ 200 < length ≤ 10FrequencyLength (cm)The class intervals in this table overlap so that it would be possible to put 10 cm, 20 cm, and 30 cm in either of two groups.Click to reveal the table correctly.An alternative would be to have class intervals of:0 < length ≤ 1010 < length ≤ 2020 < length ≤ 3030 < lengthThis is an open class interval.
12 class intervals The times roughly range from 85 to 110 seconds. The times roughly range from 85 to 110 seconds.110 – 85 = 25 seconds.Suppose we decide to use class intervals with a width of 5 seconds.25 ÷ 5 = 5 class intervals
13 Notation for class intervals How should the class intervals be written down?Times in secondsFrequency85 – 9090 – 9595 – 100100 – 105What is wrong with this table?Discuss where 90 and 105 should go. The table is ambiguous. For discrete data it would be possible to edit the table to say 86 – 90, 91 – 95, 96 – 100, 101 – 105 etc (or 85 – 89, 90 – 94 etc) but for continuous data this would not work.
14 Notation for class intervals Can you explain what the symbols in the middle column mean?100 ≤ t < 105105 ≤ t < 11095 ≤ t < 10090 ≤ t < 9585 ≤ t < 90Times in seconds85 – 90 but not including 90Frequency90 – 95 but not including 9595 – 100 but not including 100100 – 105 but not including 105Discuss where 90, 95 etc would go in this table. Represent the inequality on a number line. Ask pupils where numbers such as would go.Note that the data has been rounded off to 1 d.p. so it could be argued that we could write the intervals as 85.0 – 89.9, 90.0 – 94.9 etc but this would imply that the data is discrete, so this would be incorrect.105 – 110 but not including 110
15 Notation for class intervals 85 ≤ t < 90 means “times larger than or equal to 85 seconds and less than 90 seconds”Another way to say this is “from 85 up to but not including 90”Can you say these in both ways?1) 90 ≤ t < 95“times larger than or equal to 90 seconds and less than 95 seconds” or“from 90 up to but not including 95”.2) 105 ≤ t < 110Pupils could work together in pairs to practise the correct use of vocabulary.“times larger than or equal to 105 seconds and less than 110 seconds” or“from 105 up to but not including 110”.
16 Notation for class intervals This activity involves pupils deciding which class interval a number belongs in. The numbers should be dragged into the right interval.
17 Use the data to fill in the table. Class intervals100 ≤ t < 105105 ≤ t < 11095 ≤ t < 10090 ≤ t < 9585 ≤ t < 90Times in secondsFrequencyUse the data to fill in the table.Pupils would benefit from having a print out of the data to avoid missing out data items. A tally could be used if required.They should check they have 60 items in total in the frequency column.
18 Class intervals: Answer 100 ≤ t < 105105 ≤ t < 11095 ≤ t < 10090 ≤ t < 9585 ≤ t < 90Times in secondsFrequency1Use the data to fill in the table.5Pupils would benefit from having a print out of the data to avoid missing out data items. A tally could be used if required.They should check they have 60 items in total in the frequency column.28197
19 Which ones are you using? Creative ThinkerEffective ParticipatorIndependent EnquirerReflective LearnerSelf ManagerTeam WorkerPLT SkillsWhich ones are you using?Learning objectives reviewTo be able to design frequency tables for discrete raw data; and design data collection tables for gathering large discrete and continuous sets of raw data, choosing suitable class intervals..I don’t understandI nearly understandI fully understand
20 Effective Participator Creative ThinkerEffective ParticipatorIndependent EnquirerReflective LearnerSelf ManagerTeam WorkerLearning Objectives: To be able to design frequency tables for discrete raw data; and design data collection tables for gathering large discrete and continuous sets of raw data, choosing suitable class intervals.Assessment6b6a7c- Join up with another pupil. Discuss your answers to the task.- Have you both got the same answers? If not why?What level am I working at?
21 Level 6The possible answers are likely to range from 0 to 100, so you might draw a tally chart with groupings similar to the one below:Number of magazinesTallyFrequency0 - 45 - 9more than 49
22 Level 7You are investigating the length of time each member of a class spends on the internet per week. Look at the class groupings below - do you think they are right?Time (h)Frequency0 ≤ time ≤ 1010 ≤ time ≤ 2020 ≤ time ≤ 30These groups are wrong, because the times of '10 hours' and '20 hours' can be entered into two different groups.For example, the time 10 hours can be entered into 0 ≤ time ≤10 (where time is less than or equal to 10 hours), and also into 10 ≤ time ≤ 20 (where time is more than or equal to 10 hours).
23 Level 7Time (h)Frequency0 < time < 1010 < time < 2020 < time < 30These groups are also wrong, because the times '10 hours' and '20 hours' cannot be entered into any of the groups.For example, the time 10 hours can neither be entered into 0 < time < 10 (where time is less than 10 hours), nor can it be entered into 10 < time < 20 (where time is more than 10 hours).Time (h)Frequency0 ≤ time < 1010 ≤ time < 2020 ≤ time < 30These groupings are right. '10 hours' is included in the second group, but not the first and '20 hours' is included in the third group, but not the second.
24 Which ones are you using? Creative ThinkerEffective ParticipatorIndependent EnquirerReflective LearnerSelf ManagerTeam WorkerPLT SkillsWhich ones are you using?Learning Objectives: To be able to design frequency tables for discrete raw data; and design data collection tables for gathering large discrete and continuous sets of raw data, choosing suitable class intervals.Individual AssessmentOn your post it notes…Think about how you can improve your work.WWW (What Went Well)EBI (Even Better If)
25 Effective Participator Self ManagerIndependent EnquirerCreative ThinkerTeam WorkerReflective LearnerOn your post it.. think aboutWWW (What did you enjoy in today's lesson?)EBI (This lesson would have been better If…)