Test 2: Ch 4-6 Flashcards Preview

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Flashcards in Test 2: Ch 4-6 Deck (31):
1

Measures of Central Tendency

Categories or scores that describe what is average or typical of the distribution.

2

Mode

The category/score with the highest frequency (or %)

3

Three factors for choosing appropriate MOCT

1. The way the variables are measured.
2. The shape of the distribution.
3. The purpose of the research.

4

Bimodal

Two scores or categories with the highest frequency

5

Median

The score that divides the distribution into two equal parts so that half the cases are above it and half are below it.

6

Finding median for odd variable

(N+1)/2

7

Percentile

A score below which a specific percentage of the distribution falls.

8

Mean

A measure of central tendency that is obtained by adding up all the scores and dividing by the total number of scores. It is the arithmetic average.

9

Calculating mean

Y-bar=(Sigma)(Y)/N

10

Y

Raw scores of the variable Y

11

_
Y

The mean of Y

12

(Sigma)(Y)

The sum of all the Y scores

13

N

The number of observations/cases

14

Finding the mean in a frequency distribution

_
Y= (sigma)f (Y)/N

15

Symmetrical distribution

The frequencies at the right and left tails of the distribution are identical; each half of the distribution is the mirror image of the other.

16

Skewed distribution

A distribution with a few extreme values on one side of the distribution.

*mean, median and mode do NOT coincide. The mean falls closest to the tail of the distribution where a small number of extreme scores are located

17

Positively skewed distribution

A distribution with a few extremely high values.

18

Negatively skewed distribution

A distribution with a few extremely low values

19

Identifying shape of distribution

1. In unimodal distributions, when the mode, median, and mean coincide or are almost identical, the distribution is SYMMETRICAL.
2. When the mean is higher (or to the right) than the median, the distribution is POSITIVELY SKEWED.
3. When the mean is lower (or to the left) than the median, the distribution is NEGATIVELY SKEWED.

20

Range

Highest score - lowest score

21

Median for even

-Arrange from least to greatest
-find mean of two middles

22

Measures of variability

Numbers that describe diversity or variability in the distribution of a variable

23

Importance of measuring variability

Helps characterize and compare groups without prejudice

24

Index of qualitative variation (IQV)

A measure of variability for nominal variables.

Based on the ratio of the total number of differences in the distribution to the maximum number of possible differences within the same distribution.

25

Calculate IQV

1. Construct a percentagedistribution
2. Square the % for each category
3. Sum the squared %s
4. Calculate the IQV using the formula

26

Interquartile range IQR

The width of the middle 50% of the distribution.

The difference between lower (Q1) and upper (Q3) quartiles.

27

Box plot

1. Draw a box between the lower and upper quartiles
2. Draw a solid line within the box to mark the median
3. Draw vertical lines outside the box, extending to the lowest and highest values

28

Box Plot: symmetrical distribution

Box is in the center of the range and the median is in the center of the box.

29

Box plot: skewed distribution

Box and/or median are not centered.

Closer to Q1 when more cases have lower scores, closer to Q3 when more cases have higher scores.

30

Variance

The average of the squared deviations from the center/mean of the distribution

31

Standard deviation

The square root of the variance. Measures variability in interval-ratio variables.