Chapter 2

Question 1

frequency distribution

Answer 1

shows the number of observations for the possible categories or score values in a set of data

Question 2

class intervals

Answer 2

• grouping a range of values together (in a grouped frequency distribution)
• ex. 60-62

Question 3

raw scores

Answer 3

scores in their original form

Question 4

how to create grouped frequency distributions

Answer 4

• choose class intervals that are mutually exclusive (no overlap -> ie. no 60-63, 63-66)
• choose class intervals that are the same width apart, and include an interval even if no scores appear within it (a frequency of 0)
• place the highest value class interval at the top
• choose a convenient interval width (ie. 3, 5, 10) and use 10-20 intervals for best, most accurate results -> find this by finding the range and dividing it by 10 and by 20 to see lowest and highest acceptable widths
• make the lower score limits multiples of the interval width if possible (ie. interval width = 3, lower score limit = 60, a multiple of 3)

Question 5

range

Answer 5

difference between lowest and highest score

Question 6

symbols: i, f, n, N

Answer 6

• i: interval width
• f: frequency
• n: total number of cases in a sample
• N: total number of cases in a population

Question 7

real limits of a score

Answer 7

extend from one half of the smallest unit of measurement to below the value of the score to one-half unit above (ex. real limits of score 87 -> 86.5-87.5)

Question 8

apparent limits of a score interval

Answer 8

extend from the smallest unit of measurement in the interval to the largest (ex. 96-98)

Question 9

real (exact) limits of a score interval

Answer 9

extend from one-half the measurement unit below the lowest score to one-half the unit above the highest score (ex. 95.5-98.5)

Question 10

relative frequency distribution

Answer 10

• shows the proportion or percentage of the total number of observations for the possible categories or score values in a set of data
• to obtain proportions, divide f/n or f/N (and multiply by 100 for percentage if necessary)

Question 11

cumulative frequency distribution

Answer 11

• shows how many cases lie below the upper real limit of each class interval
• to obtain, start at the bottom and add up the frequencies until you reach the top (ex. if lowest has f of 2 -> cum f = 2; if next interval has f of 3 -> cum f = 5)

Question 12

relative cumulative frequency distribution

Answer 12

• shows proportion of cum f

- to get, divide each cum f by n or N, then convert to percentage if necessary (cum %)

Question 13

symbols: cum f, cum %

Answer 13

• cum f: cumulative frequency

- cum %: cumulative percentage

Question 14

percentile [point]

Answer 14

• point on the measurement scale below which a specified percentage of cases in a distribution fall
• ex. if 50% of students scored 81 on their exam, the 50th percentile is 81

Question 15

percentile rank

Answer 15

• percentage of cases in a distribution that falls below a given point on the measurement scale
• ex. if 50% of students scored 81 on their exam, the percentile rank of 81 is 50.

Question 16

difference between percentile points and ranks

Answer 16

• percentile ranks can only take values between 0-100
• percentile points can have any value that the scores have (ex. if a test was out of 175, a percentile point could go up to 175)