Chapter 15 A

Question 1

2 Principle purposes of statistics

Answer 1

1) to organize and summarize data–> utilizes descriptive statistics
2) justifying conclusions –> statistically test research hypothesis; utilizes inferential statistics

Question 2

2 general categories of statistics

Answer 2

descriptive and inferential

Question 3

descriptive statistics

Answer 3

summarizes data collected from the sample

Question 4

inferential statistics

Answer 4

answer general questions about a population. allows to generalize results from a sample to a population

Question 5

statistic vs parameter

Answer 5

statistics are information pieces when data is from a SAMPLE

parameter are summary values that describes a POPULATION.

Question 6

frequency distribution

Answer 6

the number of individuals/scores in each category on the scale of measurement.

Question 7

2 options for graphing numerical data (ordinal interval or ratio)

Answer 7

1) histogram, with BARS TOUCHING EACH OTHER

2) polygon- line graph

Question 8

in a histogram/bar graph that depicts nominal or ordinal statistics, should the bars touch each other?

Answer 8

no. a space should be left between adjacent bars.

Question 9

3 measures of central tendency

Answer 9

mean, median, mode

Question 10

when does a mean not provide a good measure?

Answer 10

1) when a sample has outliers

2) in nominal scales (things that cant be quantified, like names or sex)

Question 11

describing interval or ratio data

Answer 11

1) measures of central tendency
2) standard deviation, variance and range
3) sample variance and degrees of freesom

Question 12

standard deviation

Answer 12

variability of the scores by measuring the distance between EACH SCORE and the mean

Question 13

“average distnace from the mean”

Answer 13

standard deviation

Question 14

variance

Answer 14

the average squared distance from the mean

Question 15

range

Answer 15

the difference between largest value and smallest value in data set.

Question 16

when calculating degrees of freedom, why is it necessary to use n-1?

Answer 16

n-1 is an adjustment when calculating sample variance in order to provide an accurate representation of its population variance.

• normal sample variance without using n-1 UNDERESTIMATES ACTUAL VARIANCE of a population
• DOF provides more accurate and unbiased view.

Question 17

Empirical rule

Answer 17

68-95-99.7

Question 18

factorial research study

Answer 18

includes 2 or more independent variables (ex/ temperature and humidity (IVs) on performance (DV))

Question 19

how can a factorial research study be represented

Answer 19

via matrices

Question 20

Correlation

Answer 20

statistical value that measures and describes the direction and degree of relationship between 2 variables ranked from -1 to +1

Question 21

pearson correlation

Answer 21

evaluates linear relationships- if the data is interval or ratio, spearman correlation can be determined in order to measure the degree to which the relationship is ONE-DIMENSIONAL and not influenced by other factors.

Question 22

regression

Answer 22

the equation of the straight line. (slope)

Question 23

multiple regression:

Answer 23

when 2 variables are used to predict Y

Question 24

Internal consistancy

Answer 24

refers to the extent to which the scores on the items correlate with each other. do the questions on the test measure the same thing?

Question 25

What formula does split-half reliability use?

Answer 25

spearman brown formula R= (2r)/1+r

where r= correlation between the two halves of the test
R=reliability

and kuder-richardson formula #20