Introductory Statistics for Laboratorians dealing with High Throughput Data sets Centers for Disease Control

Shapes of Distributions

Uniform Distribution

Density curves come in any imaginable shape. Some are well-known mathematically and others aren’t.

Problem 6 Scores: 9, 8, 8, 7, 6, 5, 5, 5, 4, 3 How many scores are there? N = ________. Make a frequency distribution using the table provided. Make a bar chart of the data using the axes provided.

Problem 6 Frequency Distribution Scores X Frequency f N =

Problem 6 Frequency Distribution Scores X Frequency f N =

Problem 6 Bar Chart

Problem 6 Central Tendency Which score is most frequent? Draw a line on the bar chart that splits the distribution in half (ie: half the scores are above the line, half are below the line). Calculate the average of the 10 scores. (Scores are repeated here: 9, 8, 8, 7, 6, 5, 5, 5, 4, 3 )

Definitions: Central Tendency There are three different statistics that are used to indicate the center/middle of the distribution. They are: Mode: the most frequent score (M o ) Median: the score that splits the distribution in half (half the scores above/ half below). (M d ) Mean: the arithmetic average. ( )

Central Tendency In a Symetrical Distribution

Skewness Negatively skewed distribution

Skewness Positively Skewed

Kurtosis

Examples