Unit 2

Question 1

Percentile

Answer 1

The percent of values in a distribution that are less than or equal to the individual’s data value

Question 2

Cumulative Relative Frequency Graph

Answer 2

Plots a point corresponding to the percentile of a value in a data set

Consecutive points are connected with line segments

Question 3

Standardized score (z-score)

Answer 3

The # of SD’s a data value is above or below the mean in a distribution

Formula:
Z=Value — Mean / Standard Deviation

Question 4

Z-Score tips

Answer 4

Make sure you report the # of SD’s and the direction

Larger z-scores aren’t always “better”

Question 5

Effect of Adding or Subtracting a Constant

Answer 5

Adds X to measures of CENTER and LOCATION

Does NOT change measures of spread

Won’t change shape

SEE PAGE 6

Question 6

Effect of Multiplying or Dividing a Constant

Answer 6

Multiplies measure of CENTER and LOCATION by Z

Multiplies measures of SPREAD by Z

Does NOT change SHAPE

SEE PAGE 6

Question 7

Density Curve

Answer 7

Models the shape of a distribution

Always above the X-axis

Total area is equal to 1

SEE PAGE 9

Question 8

Mean & Median (density curves)

Answer 8

Median “Equal Area Point” is the point that divides curve into 2 equal area region

Mean “Balance Point” is the on x-axis that balances the curve if it were a solid material

Question 9

Normal Curves

Answer 9

Shape: Symmetric, unimodal, Bell shape

Center: Mean=Median (In the middle)

Spread: SD, measures width of the curve
DONT FORGET
Empirical rule: 68- 95- 99.7

Question 10

Normal Distribution

Answer 10

Symmetric, Bell-shaped, unimodal and defined by its Mean (μ) and its SD (σ)

Question 11

The Empirical Rule

Answer 11

68% of data values in a normal distribution are within one SD of the mean

95% of values fall within 2 SD’s
99.7% of values fall within 3 SD’s

Question 12

Normal Distributions

Answer 12

The STANDARD normal distribution is a normal distribution with:
Mean=0
SD=1
(This is because the distribution is in Z-scores)

Question 13

How to find areas

Answer 13

Step 1:
Draw normal distribution, scale x-axis, mark the mean and 3SD’s above/below, then shade area of interest
Step 2: Do calculation using either Table A or calculator
Step 3: Be sure to answer with a full sentence

Question 14

How to find values from areas in any normal distribution

Answer 14

Step 1:
Draw a curve, label X-axis, shade given area
Step 2: Use Table A or “Inv Norm” on calc
Step 3: Be sure to answer with full sentence