Statistics - Chapter 2

Front 1

grouped frequency distribution

Back 1

when the range of the data is large, the data must be grouped into classes that are more than one unit in widthe

Front 2

give example of grouped frequency distribution

Back 2

height ranges are classes that must be used

Front 3

lower class limit

Back 3

represents the smallest data value that can be included in the class

i.e. 50 in range of 50- 59

Front 4

upper class limit

Back 4

the largest data value that can be included in the class

i.e. 59 in range of 50-59

Front 5

class boundaries

Back 5

used to separate the classes so that there are no gaps in the frequency distribution
in range of 49 to 59 and 59
i.e. lower boundary = -.5
upper boundary = +.5
49.5 - 59.5
59.5 - 69.5

Front 6

dependent (response) variable

Back 6

measures the outcome of interest

Front 7

independent (explanatory) variable

Back 7

the variable that explains the response

Front 8

i.d. the explanatory and response variables in the following:
smoking leads to lung cancer
final grade in a class and amount of work completed

Back 8

explanatory = smoking
response = lung cancer

expl. = amount of work
response = final grade

Front 9

confounding variable

Back 9

a variable that influences the outcome of an experiment but can't be separated from the explanatory variable.

Front 10

give an example of a confounding variable

Back 10

study of age and heart attacks

everything else that could explain heart attacks besides age is a confounding variable.

Front 11

raw data

Back 11

when data are collected in original form

Front 12

class

Back 12

a quantitative or qualitative category into which each raw data value is placed

Front 13

frequency

Back 13

number of data values that fall into a specific class

Front 14

proportion

Back 14

the frequency of observations in a specific class divided by the total number of observations

Front 15

percentages

Back 15

the proportion multiplied by 100 (move the decimal point two places to the right)

Front 16

frequency distribution

Back 16

the organization of raw data in table form, using classes, frequencies and sometimes proportions and percentages

Front 17

histogram

Back 17

a graph that displays the data by using continuous vertical bars of various heights to represent the frquencies of the classes (for quantitative)

Front 18

steps to construct a histogram

Back 18

draw and label
y axis = frequencies
x axis = class boundaries

using the frequency as the heights, draw vertical bars for each class

Front 19

frequency polygon

Back 19

a graph that displays the data by using lines that connect points plotted for the frequencies at the midpoints of the classes. The frequencies are represented by the heights of the points.

Front 20

steps to construct a frequency polygon

Back 20

1. find the midpoints of each class (midpoint = upper boundary + lower boundary then divide by 2)
2. draw x axis (midpoint) and y axes (frequency)
3. using the midpoints for the x values and the frequencies as the y values, plot the points.
4 connect adjacent points with line segments. Draw a line back to the x axis at the beginning and end of graph

Front 21

ogive

Back 21

graph that represents the cumulative frequencies for the classes in a frequency distribution

Front 22

1st step in ogive

Back 22

find cumulative frequency for each class

Front 23

2nd step in ogive

Back 23

draw s axis (class boundaries) and y axis (cumulative frequency)

Front 24

3rd step in ogive

Back 24

plot the cumulative freqency at each UPPER class boundary

Front 25

4th step in ogive

Back 25

starting with the first upper class boundary, connect adjacent points with line segments. extend the graph to the first lower class boundary on the x axis

Front 26

bell-shaped

Back 26

symmetric curve with one peak

Front 27

uniform graph

Back 27

flat and rectangular

Front 28

skewed

Back 28

not symmentrical and is slightly shifted to the right or the left

Front 29

j-shaped

Back 29

similar in shape to skewed left but strictly increases as you move to the right = always going up

Front 30

reverse j-shaped

Back 30

similar in shape to skewed right but stricly increases as you move to the left

Front 31

bimodal

Back 31

graph with exactly 2 peaks

Front 32

u-shaped

Back 32

higher on the end, lower in the center