Exam 3

Question 1

Frequency Distribution

Answer 1

Is an organized tabulation of the number of individuals in each category on the scale of measurement.

Question 2

Absolute Frequency (f)

Answer 2

The number of participants that fall in each category.

Question 3

Relative Frequency (rf)

Answer 3

The proportion of participants that fall in each category.

-f/N where N=total number of scores

Question 4

Percent

Answer 4

rf*100

Question 5

Cumulative Frequency (cf)

Answer 5

The number of people that score AT or LOWER than a given score.

Question 6

Cumulative Relative Frequency (crf)

Answer 6

• Use rf column

- Proportion of people that scored AT or BELOW a given score.

Question 7

Cumulative Percent

Answer 7

crf*100

Question 8

Real Limits and Frequency Distributions

Answer 8

Begin 1 unit below lowest score and end 1 unit above highest score.

Question 9

Frequency Graphs

Answer 9

• Grouped or Ungrouped (interval) Scores

- Used when you have discrete variables

Question 10

Frequency Histogram

Answer 10

No spaces or gaps between bars.

-Used when the data consist of numerical scores that have been measured on an interval or ratio scale.

Question 11

Frequency Polygon

Answer 11

Dots connected by a continuous line that begins and ends on the x-axis.
-Used when the data consist of numerical scores from an interval or ratio scale.

Question 12

Bar Graph

Answer 12

Much like a histogram, except there are spaces between the bars.
-Used with nominal and ordinal scales.

Question 13

Symmetrical Distribution

Answer 13

It is possible to draw a line down the middle so that one side of the distribution is a mirror image of the other.

Question 14

Skewed Distribution

Answer 14

The scores tend to pile up toward one end of the scale and taper off gradually at the other end.

Question 15

Positively Skewed Distribution

Answer 15

When the scores pile up on the left side of the distribution. The tail points toward the positive end of the x-axis (right).

Question 16

Negatively Skewed Distribution

Answer 16

When the scores pile up on the right side of the distribution. The tail points toward the negative end of the x-axis (left).

Question 17

Line Plot

Answer 17

Same as polygon, but left and rightmost points are NOT closed at the abscissa.

Question 18

Stem and Leaf

Answer 18

Obtains the raw data in the display.

Question 19

Tukey’s Tallies

Answer 19

Does not maintain raw data.

Question 20

Heuristic for Grouping Scores

Answer 20

1) Determine the number of groups
- 5-15
2) Determine the size (width) of the interval (2,3, or some multiple of 5)
- Highest score-Lowest score
- Divide by number of groups
- Round to nearest commonly used interval size
3) Determine the beginning lowest interval (should be a multiple of width)

Question 21

Measures of Central Tendency

Answer 21

Mode, Median, Mean

Question 22

Mode

Answer 22

Most commonly occurring score.
Advantages: score that actually occurs in the data set, unaffected by extreme scores, represents most common observation
Disadvantage: may not be representative of entire distribution of scores

Question 23

Median

Answer 23

Divides the distribution into equal halves.
(N+1)/2=Median Location
Advantages: takes into account all the data in the distribution, unaffected by extreme scores (use when distributions are skewed), use if have missing values in data set, open-ended distribution, use with an ordinal scale
Disadvantages: value may not exist in the data, does not enter readily into equations and more difficult to work with, treats all scores alike; differences in magnitude not taken into account

Question 24

Mean

Answer 24

Arithmetic average of scores.
Advantages: representative of every score in the distribution, closely related to variance and standard deviation
Disadvantages: affected by extreme scores or “outliers” when you have only a limited number of scores in your distribution, value may not exist in data

Question 25

Central Tendency

Answer 25

An attempt to find a single score that represents the center of a distribution. Strives to find a number representative of the whole distribution.

Question 26

Variability

Answer 26

A qualitative measurement of the differences between scores and the degree to which they are different. Are they spread out or clustered?

Question 27

Biased Variance

Answer 27

An average value of the statistic that is equal to the population parameter.

Question 28

Unbiased Variance

Answer 28

An average value of the statistic that either over or underestimates the corresponding population parameter.

Question 29

Sum of Squares

Answer 29

How each score varies from the mean.
Advantage: takes into account ALL the scores in a distribution.
Disadvantage: size of SS depends on the amount of variability and is influenced by N.

Question 30

Population Variance

Answer 30

Average of the SUM of squared deviations from the mean (Mean Squared Distance).
-Takes into account N.

Question 31

Population Standard Deviation

Answer 31

Represents an average distance or direction from the mean.

Question 32

Sample Variance

Answer 32

Average SUM of squared deviations from the mean.

-Takes into account n.

Question 33

Standard Deviation

Answer 33

Represents an average distance or direction from the mean.