Unit 1

Question 1

Number of units in a sample:

Answer 1

Sample size (n).

Question 2

Quantitative variable:

Answer 2

Anything that can be measured numerically.

• A person’s height.
• The weight of a dog.
• The time it takes to drive to work.

Question 3

Categorial variable:

Answer 3

• Nominal: Data is recorded as labels.
  
  • Gender.
  • Marital status.
  • License plates.
• Ordinal: Data follows a “natural” order and makes sense.
  
  • Birth month for people born in 1996.
  • Service rating of a restaurant.

Question 4

To show categorial variables we can use ____________.

Answer 4

• Bar charts.

- Pie charts.

Question 5

To show quantitative variables we can use ____________.

Answer 5

• Histograms.

- Stem and leaf plots.

Question 6

How do you find the range of values?

Answer 6

Maximum - minimum data value.

Question 7

Define: Mean.

Answer 7

The average value. (Add up everything and divide by n)

Question 8

Define: Median.

Answer 8

The middle value. (To find the location of the median: n+1/2)
Note that this just the location

Question 9

Define: Outlier.

Answer 9

A point that falls far away from the majority of the data.

Question 10

The median is _____ to outliers, while the mean is _____ to outliers.

Answer 10

Robust, not robust.

Question 11

When a histogram is skewed to the left, it implies that the mean is _____ than the median.

Answer 11

Less.

Skewed to the left means the tail is on the left end.

Question 12

When a histogram is skewed to the right, it implies that the mean is _____ than the median.

Answer 12

Greater.

Skewed to the right means that the tail is on the right end.

Question 13

Interquartile range (IQR):

Answer 13

A measure of spread, covering the middle 50% of ordered data.

• To find Q1: Find the median, and then the median of your results (from smallest, to your median).
• To find Q3: Find the median, and then the median of your results (from largest, to your median).

Question 14

How to interpret percentiles:

ie. I am in the 60th percentile for height, what does this mean?
ie. I score in the 80th percentile on an exam, what does this mean?

Answer 14

• Being in the 60th percentile means that 40% of the population is as tall, or taller than me.
• Scoring in the 80th percentile means that 20% did as good, or better than me on the exam.

Question 15

What is included in the 5 number summary?

Answer 15

• Minimum
• First quartile
• Median
• Third quartile
• Maximum

Question 16

What is a boxplot?

Answer 16

Includes the 5 aspects of a 5 number summary in a visual form. Outliers represented as an asterisk.

Question 17

How do you calculate standard deviation (s)?

Answer 17

• Find the mean of the data.
• Subtract the mean from every data value.
• Square those results.
• Sum them all.
• Divide by n-1.
• Take the square root.

Question 18

How do you calculate variance (s^2)?

Answer 18

Just square the standard deviation.