Descriptive Statistics

Question 1

Statistics is a way of doing what?

Answer 1

summarizing/organizing and interpreting data

Question 2

What is a statistic?

Answer 2

a number obtained from mathematical manipulation of the raw data

Question 3

Descriptive statistics

Answer 3

describe characteristics of data

Question 4

3 key goals of descriptive statistics

Answer 4

organize data into a usable form
describe key features
summarize data without making inferences about a larger population

Question 5

______ and _______ data are discrete

Answer 5

nominal
ordinal

Question 6

Grouping the nominal data is

Answer 6

counting the number/frequency of cases falling into each category

Question 7

Table conventions for nominal data

Answer 7

table must be clearly and fully labeled

Question 8

Nominal data: f = ???

Answer 8

frequency of cases

Question 9

Nominal data: n = ???

Answer 9

total number of cases or measurements in a study sample

Question 10

Nominal data: N = ???

Answer 10

number of cases in population

Question 11

Visualization of discrete data: Discrete data often plots _________ distributions of ________ data as what?

Answer 11

frequency
qualitative
bar graphs or pie diagrams

Question 12

What does a bar graph involve

Answer 12

plotting the frequency of each category and drawing a car

Question 13

Conventions in plotting bar graphs: y axis

Answer 13

used to plot frequencies

Question 14

Conventions in plotting bar graphs: x axis

Answer 14

used to indicate the categories

Question 15

Conventions in plotting bar graphs: bars dont ___________ reflecting what?

Answer 15

touch each other
discontinuity of data

Question 16

Bar graphs can also be plotted as what instead of frequencies?

Answer 16

percent

Question 17

Clustered bar graph

Answer 17

graphing experimental and control group on the same graph

Question 18

Visualization of discrete data: Pie diagram

Answer 18

% of each category as a piece of pie

Question 19

Organization and presentation of interval or ratio data: real numbers

Answer 19

can be processed mathematically

Question 20

Interval or ratio data often produce what?

Answer 20

continuous data (weight, length, time, IQ)

Question 21

Step 1 of constructing a grouped frequency distribution

Answer 21

organize data into ordered array of score frequencies

Question 22

Step 2 of constructing a grouped frequency distribution

Answer 22

find ranges of scores: highest - lowest +1

Question 23

Step 3 of constructing a grouped frequency distribution

Answer 23

decide on width (i) of the class intervals

Question 24

Step 4 of constructing a grouped frequency distribution

Answer 24

note limits of each class interval

Question 25

Step 5 of constructing a grouped frequency distribution

Answer 25

count frequency of scores in each class interval and tabulate

Question 26

True or false: the final grouped data of frequency distributions is much easier to interpret than original raw data

Answer 26

true

Question 27

Final grouped frequency distributions lose some what?

Answer 27

precision in the data

Question 28

3 conventions for grouped frequency distributions

Answer 28

not too few or too many groups/classes equally sized class intervals midpoint of class interval represents the class interval

Question 29

If there are too many groups/classes in grouped frequency distributions what happens

Answer 29

it is difficult to inspect

Question 30

If there are too few groups/classes in grouped frequency distributions what happens

Answer 30

meaning of the varied data is lost

Question 31

Qualitative data of frequency distributions are often plotted as

Answer 31

histograms or frequency polygons

Question 32

Histograms

Answer 32

like bar graphs but bars touch each other to reflect continuity of data

Question 33

In histograms what to the midpoint and width of the bar correspond to

Answer 33

the midpoint and width of the class interval

Question 34

Frequency polygons

Answer 34

same as histogram (bars touch each other) but plot a line through midpoint of each class interval, at a height representing the frequency of the scores

Question 35

What do frequency polygons allow the reader to do?

Answer 35

interpolate/estimate the frequency of values in between those actually measured or graphed

Question 36

Frequency polygons can take on what 3 shapes

Answer 36

bell shaped - normal distribution negatively skewed - mean to left of normal positively skewed - mean to right of normal

Question 37

After summarizing data in frequency distribution it is often useful to do what?

Answer 37

compare relative frequencies of different categories

Question 38

Comparing relative frequencies of different categories is useful for

Answer 38

understanding comparative trends in the data

Question 39

Comparing relative frequencies of different categories can be used on what?

Answer 39

any scale

Question 40

Calculation of statistics allow what?

Answer 40

"crunching" raw data into single numbers that summarize the data

Question 41

Ratios

Answer 41

relative frequency of one set of frequencies to another

Question 42

Proportion

Answer 42

frequency of one category relative to total sample or population

Question 43

Rates in epidemiology are useful for what?

Answer 43

representing level at which a disease is present in a given population

Question 44

Incidence rate =

Answer 44

(number of new cases/total population at risk) x base (ex. 1,000 or 100,000)

Question 45

Prevalence rate =

Answer 45

(number of existing cases/total population at risk) x base

Question 46

2 useful statistics for representing sample data

Answer 46

measures of central tendency measures of dispersion/variability

Question 47

Measures of central tendency

Answer 47

statistics or numbers expressing most typical or representative scores in a data distribution

Question 48

Measures of dispersion/variability

Answer 48

statistics representing the extent to which scores are dispersed or spread out numerically

Question 49

3 measures of central tendency

Answer 49

mean median mode

Question 50

What is the mean and what is it used for

Answer 50

average of the data for interval or ratio data

Question 51

What is the median and what is it used for

Answer 51

score that divides the distribution in half for ordinal, interval, or ratio scale data

Question 52

What is the mode and what is it used for

Answer 52

most frequently occurring score used for nominal data

Question 53

The mode can also be calculated for what data?

Answer 53

continuous data

Question 54

Sample mean

Answer 54

sum of all the data points in the sample/the number of data points in the sample

Question 55

Population mean

Answer 55

sum of all data points in the population/the total number of data points in the population

Question 56

Formula to calculate median

Answer 56

(n + 1)/2 and count to that number in the ordered array

Question 57

If n is odd the median is

Answer 57

the middle score

Question 58

If n is even the median is

Answer 58

midway between (average of) two middle scores

Question 59

For skewed continuous data ________ may be more suitable than ________ for representing the "________" score

Answer 59

median mean typical

Question 60

Three statistics for dispersal are

Answer 60

range variance standard deviation

Question 61

Range

Answer 61

difference between highest and lowest scores

Question 62

Range is easy to calculate but

Answer 62

dependent on only two extreme scores, not typical dispersal

Question 63

Average deviation is about the _______

Answer 63

mean

Question 64

Average deviation would be a convenient measure of __________

Answer 64

variability

Question 65

When you solve a problem with squaring the deviations this is called what?

Answer 65

sum of squares

Question 66

When calculating the standard deviation, the larger the standard deviation the

Answer 66

more spread out the scores about the mean