Essentials of Statistics for the Behavioral Sciences Ch.3

Unlike mean & median, what can there be more than 1 of?

Mode

What is the only measure of central tendency that is always an actual score from your data set?

Mode

What is least & most affected by outliers?

Mode & Mean

Mean (pg. 61)

Calculated by adding up all the scores in the distribution & dividing by the number of scores. -average

Weighted Mean (pg. 64)

Combined mean of 2 separate set of scores, calculated by adding up all the scores from BOTH data sets & divide by the total number of scores in BOTH data sets.

When would adding/removing NOT change the mean?

If the score was exactly equal to the mean.

Outliers

In skewed distributions, it's the extreme values in the tail

What will happen if the value of any score is changed?

It will change the mean.

Weighted Mean (Formula) (pg. 64)

M = (∑X1 + ∑X2) / (n1 + n2) *note that this is for a sample

Sample Mean (Formula)

M = ∑X/ n

What are 3 kinds of central tendency?

Mean, Median & Mode

Central Tendency (General Term)

Single value that accurately describes the center of the distribution & represents the entire distribution of scores. (Aka "the average")

Central Tendency

Statistical measure that attempts to determine the single value/ how a data set/collection of scores can be summarized using a single number.

What if there was an even number of scores?

Take the mean of the middle 2 scores.

Symmetrical Distribution (pg. 80)

The right hand side of the graph is a mirror image of the left hand side

Mode (pg. 73)

The score/tendency that has the greatest frequency/ most occurring score. -use the mode with nominal scales, discrete variables, describing shape

Median (pg. 69)

When the scores in a distribution are listed in order of smallest-largest, the median is the midpoint of the list.

Skewed Distributions (pg.81)

especially distributions for continuous variables, there is a strong tendency for the mean, median, and mode to be located in different positions

Mean as a balance point

the mean can never be outside the range of scores

Population Mean (Formula)

μ = ∑X / N