Statistics Summary Notes

Lesson One-Percentiles

Percentile Rank-tell's us the percentage of all scores that fall below a particular score.

P.R=B+0.5E*100/n

B= Below a given score
E= Equal to the given score, including the given score
N= total number of raw scores

Lesson 2: Measures of Variability- Standard Deviation

Range- in a set of numbers os the difference between the largest and the smallest numbers in a set.

Step 1: Determine the mean.
Step 2: Determine the difference between each score, and the mean.
Step 3: Determine the square of each of these differences.
Step 4: Determine the sum of the squares.
Step 5: Divide the sum of the squares by n-1
Step 6: The standard diviation, calculate square root of this number.

Lesson 3- Normal Distibution

Characteristics of the Normal Curve:

1: Bellshaped- infinite in both directions
2: Symmetric about the mean.
3: Median ( middle number)
4: approxiatemly all of the data.

Lesson 4: Correlation Coefficient

Interpret a number that measures a relationship between two sets of values is the correlation coefficient or r.

Three ways that data can be described on a scatterplot:

1: Positive Correlation- means that as one variable increases, another variable also increases, or thats as one variable decreases, another variable decreases as well. Positive Correlation falls between the values 0 and +1.

2:Negative Correlation- means that as one variable increases, another variable decreases, or that as one variable decreases, another variable increases. It falls between 0 and -1.

3: Zero Correlation- means that the variable in question essentially have nothing to do with each other and, therefore, cannot be said to be related. It's very close to or equal to 0.