Chapter 2: Frequency Distributions Flashcards

1
Q

Frequency Distribution

A

An organized tabulation showing how many individuals are located in each category on the scale of measurement

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2
Q

Frequency Distribution Table

A

Consists of at least two columns-one listing categories on the scale of measurement (X) and another for frequency (f)

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3
Q

Making a Frequency Distribution Table

A
  1. Decide the bins
  2. Decide the upper and lower limits of the bins (related to the real limits we discussed in chapter 1)
  3. Put your data in the bins
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4
Q

Proportions (Relative Frequencies)

A

Measures the fraction of the total group that is associated with each score
Proportion = p = f/N

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5
Q

Percentage

A

Find the proportion (p) then multiply by 100
Percentage = p(100) = f/n (100)

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6
Q

Cumulative Frequencies

A

The accumulation of individuals as you move up the scale
Adding up the frequencies in and below that category
Cf = (c%/100) (N)

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7
Q

Cumulative Percentages

A

The accumulation of percentages as you move up the scale
The percentage of individuals who are located in and below that category
c% = cf/N (100%)

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8
Q

Pecentiles

A

The percentage of individuals in the distribution with scores at or below the particular value

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9
Q

Finding Percentile

A
  1. Go back to the original data
  2. Put it in order
  3. Use this formula to sort out what data point is in the percentile you want:
    = (c%/100) * (n)
  4. Plug it in
    Ex. 50th percentile = (50/100) * 12 = 6
  5. Go to that position in the ranked data. (counting from lowest to highest)
    * Round UP to the nearest whole number
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10
Q

Class intervals

A

Groups of scores

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11
Q

Grouped Frequency Distribution

A

Presents groups of scores in a table rather than individual values

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12
Q

Rules for creating class intervals

A
  1. Width of the each interval should be relatively simple (ex. 2, 5, 10, 20)
  2. The bottom score should be a multiple of the width (ex. Width of 10 points = intervals should start with 10, 20 etc.)
  3. All intervals should be the same width
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13
Q

What frequency distribution graph to use?

A

Continuous variables: use histogram or polygon
Discrete variables (not numbers): use a bar graph

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14
Q

Histogram vs. Bar graph

A

Histogram = no spaces between bars (demonstrates they are continuous)
Bar graph = spaces between bars (demonstrates they are separate categories)

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15
Q

Symmetrical distribution

A

it is possible to draw a vertical line through the middle so that one side of the distribution is a mirror image of the other

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16
Q

Skewed distribution

A

the scores pile up toward one end of the scale and taper off gradually at the other end

17
Q

Positive skew

A

tail on the right

18
Q

Negative skew

A

tail on the left

19
Q

Tail

A

the section where the scores taper off

20
Q

Calculating ∑x from frequency distributions

A

Use all the information from the table (use info in both the f and x columns)
Multiply each x value by its frequency then add the products

21
Q

Calculating the number of rows

A

rows = highest - lowest +1