Chapter 5: The Standard Deviation as a Ruler and the Normal Model

Question 1

Percentile

Answer 1

The percent of data less than or equal to a certain data value
“The value of ____ is at the (p)th percentile. About (p) percent of the values are less than or equal to ____.”

Question 2

Standardized Score (Z Score)

Answer 2

Measures how many standard deviations a data point is below or above the mean
([data point - mean]/standard deviation)
“The value of ____ is (z-score) standard deviations (above/below) the mean.”

Question 3

Standardization

Answer 3

A point’s location in the distribution depends on both distance from the mean and the distribution’s spread

Question 4

Normal Distribution

Answer 4

1. Bell curve; symmetric
2. Many quantitative variables in the real world can be modeled by a normal distribution (height, temperature, blood pressure)
3. Determined by the mean (μ) and the SD (σ)

Question 5

Empirical Rule

Answer 5

68% of values fall within 1 SD of the mean
95% of values fall within 2 SDs of the mean
99.7% of values fall within 3 SDs of the mean