Starting out with Statistics

What do we do with statistics? Describe a group using numbers Descriptive Statistics Infer about how a larger group of data would behave based on a smaller subset. Inferential Statistics A set of rules that help us make a decision about how good an inference we can make.

Some terms to start off Population: Sample: All the data points that could be considered Sample: The data points that are being evaluated Usually less than the population (a subset of the population) Often a good representation of the population

Some terms to start off Variable Dependent variable: A particular piece of information that can take on different values across the data that is being evaluated. Dependent variable: Typically what the investigator is interested in measuring Independent variable: Typically the way in which the data is grouped, or what is being manipulated.

Frequency Table A column for the variable A column for frequency (test scores) A column for frequency (number of subjects who received a particular score)

grades 30 3 29.5 5 29 28.5 2 28 10 27.5 27 6 26.5 26 25 24.5 24 4 23.5 1 23 22.5 22 21.5 21 20

Frequency Table Cummulative frequency Number of subjects who have a particular score or any that are lower (or higher)

grades 30 3 29.5 5 29 28.5 2 28 10 27.5 27 6 26.5 26 25 24.5 24 4 23.5 1 23 22.5 22 21.5 21 20

grades 30 3 29.5 5 29 28.5 2 28 10 27.5 27 6 26.5 26 25 24.5 24 4 23.5 1 23 22.5 22 21.5 21 20

grades 30 3 29.5 5 29 28.5 2 28 10 27.5 27 6 26.5 26 25 24.5 24 4 23.5 1 23 22.5 22 7 21.5 21 20

grades 30 3 73 29.5 5 70 29 65 28.5 2 60 28 10 58 27.5 48 27 6 43 26.5 37 26 32 25 24.5 24 4 21 23.5 1 17 23 16 22.5 11 22 7 21.5 20

grades 30 3 73 29.5 5 70 29 65 28.5 2 60 28 10 58 27.5 48 27 6 43 26.5 37 26 32 25 24.5 24 4 21 23.5 1 17 23 16 22.5 11 22 7 21.5 20

If you wanted to find what would you do?

grades 30 3 29.5 5 29 28.5 2 28 10 27.5 27 6 26.5 26 25 24.5 24 4 23.5 1 23 22.5 22 21.5 21 20

grades 30 3 90 29.5 5 29 28.5 2 28 10 27.5 27 6 26.5 26 25 24.5 24 4 23.5 1 23 22.5 22 21.5 21 20

grades 30 3 90 29.5 5 147.5 29 28.5 2 28 10 27.5 27 6 26.5 26 25 24.5 24 4 23.5 1 23 22.5 22 21.5 21 20

grades 30 3 90 29.5 5 147.5 29 145 28.5 2 57 28 10 280 27.5 137.5 27 6 162 26.5 132.5 26 156 25 50 24.5 73.5 24 4 96 23.5 1 23 115 22.5 22 21.5 43 21 20 60

ƒ Test scores

Symmetric Distribution: A distribution in which the left and right halves are mirror images.

Frequency how many Scores

Symmetric frequency scores

Skewed Distribution: The majority of the scores in the distribution fall to one end. At the opposite end of the distribution is a tail.

frequency scores

frequency scores