Statistical Reasoning

Question 1

Z scores

Answer 1

1. # of standard deviations of a value above the mean

2. Z score= (Score) - mean / standard deviation

Question 2

Normal Distribution

Answer 2

1. Between M and M + 1S is 34% of population.
2. Between (M + 1S) and (M + 2S) is 13.5%.
3. Between (M + 2S) and (M + 3S) is 2.5%
4. mean = median, so 50 % above and below mean.

Question 3

Precision vs Accuracy

Answer 3

1. Precision: measurement about spread.
2. Accuracy: measurement about the mean.
   - low precision, high accuracy= random errors.
   - high precision, low accuracy= systematic errors.
3. Imprecise data called “highly variable.”
4. Inaccurate data called “skewed.”

Question 4

Standard Deviation

Answer 4

“Deviation from the mean.”

1. How far away from the mean are the individual data points?