Descriptive Statistics

Question 1

___________________ techniques include tables, frequency distributions, frequency polygons, measures of central tendency, and measures of variability.

Answer 1

Descriptive.

Question 2

When using a frequency polygon, scores are recorded on the _______________ axis (abscissa), while frequencies are coded on the _________________ axis (ordinate).

Answer 2

• Horizontal
• Vertical

Question 3

_______________ refers to the relative peakedness of a distribution;

• _______________: Distribution is MORE peaked than normal
• _______________: Distribution is LESS peaked than normal
• _______________: Distribution is normal

Answer 3

• Kurtosis
• Leptokurtic
• Platykurtic
• Mesokurtic

Question 4

__________________ skewed distribution: Most of the scores are in the negative (low score) side of the distribution.

Answer 4

Positively.

Question 5

______________________ skewed distribution: Most of the scores are in the positive (high score) side of the distribution.

Answer 5

Negatively.

Note: “The tail that tells the tale.”

Question 6

Measures of Central Tendency:

• ______________: The score or category that occurs most frequently; can have more than one; is susceptible to sampling fluctuations
• ______________: Divides a distribution in half when the data have been ordered from low to high; is insensitive to outliers
• ______________: (M or X-bar) the arithmetic average (M=ΣX/N); least susceptible to sampling fluctuations, but is affected by the magnitude of every score in the distribution

Answer 6

• Mode
• Median
• Mean

Question 7

The ________________ is the preferred measure of central tendency when the data is on an ordinal scale; the _________________ is preferred for interval and ratio scales.

Answer 7

• Median
• Mean

Question 8

Measure of Central Tendency (from greatest to least) for skewed distributions:

• ________________ skewed: Mean, Median, Mode
• ________________ skewed: Mode, Median, Mean

Answer 8

• Positively
• Negatively

Question 9

________________ is calculated by subtracting the lowest score in the distribution from the highest score.

Answer 9

Range.

Question 10

Variance is calculated using the following formula:

S² (Variance) = SS = Σ(X-M)²

N-1 N-1

Where:

• SS = the _________________, which is calculated by subtracting the mean from each score to obtain deviation scores, squaring each deviation score, and then summing the squared deviation scores
• N-1 = the _______________ minus 1 (when calculating sample variance; N when calculating population variance)

Answer 10

• Sum of Squares
• Number of observations

Question 11

The ____________________ is more often used as a measure of variability, and is calculated by taking the square root of the variance, which converts it to the same unit of measurement as the original scores:

S = Square Root (SS/N-1)

Answer 11

Standard Deviation.

Question 12

Identify the Areas Under the Normal Curve:

• 1 to +1 SD: ___________%
• 2 to +2 SD: __________%
• 3 to +3 SD: __________%

Answer 12

• 68.26%
• 95.44%
• 99.72%

Question 13

When a constant is added/subtracted to every score in a distribution, the measures of __________________ change, but the measures of _______________ do not. However, when each score is multiplied or divided by a constant, measures of both central tendency and variability are affected.

Answer 13

• Central tendency
• Variability