Distributions

Question 1

Histogram

Answer 1

Y axis- frequency.
X Axis- measure variables/categories.
Bars are joined because they represent continuous group of scores.
Always equal widths.

Question 2

Stem and leaf

Answer 2

Stem- 10s.
Leaf- units.
Small samples not as nest of a distribution.

Question 3

Normal distributions

Answer 3

Mean and median are almost the same.
Scored lie within -/+ 3 standard deviations of the mean.
Bell shaped, symmetrical.

Question 4

Normal distribution std devs

Answer 4

• /+ 1 std dev = 68.26%.
• /+ 2 std dev = 95.44%.
• /+ 3 std dev = 99.74%.

Question 5

Kurtosis

Answer 5

Mesokurtic curve- average.
Leptokurtic curve- small std dev; tall and squished.
Platykurtic curve- large std dev; flat and squashed.

Skewed- Negative; positive.
Bimodal.

Question 6

Z scores

Answer 6

Identify individual positions along the curve.
Allows comparisons of different tests.
Converts a score to a z score.
Z score = score - mean / std dev.

Question 7

Box and whisker plots

Answer 7

Shows distribution of scored but clearly identifies extreme scores. Based on ordinal data.
Shows interquartile range.

Question 8

Samples and populations

Answer 8

Sample statistics- descriptive measures obtained from sample group.
Population parameters- same descriptive measured estimated for whole population.
Sampling error- samples won’t produce exactly accurate stats for the population; larger the sample the more accurate.