M3: Measures of Center and Variability

Question 1

3 Measures of Center

Answer 1

a) Mean - Average of all the observations
b) Median - Observation right in the middle
c) Mode - Most frequently occured value

Question 2

3 Measures of Variability

Answer 2

a) Range
b) Variance
c) Standard deviation

Question 3

Range

Answer 3

MAX - min

Question 4

Variance (s^2)

Answer 4

s^2 = sum((x-xi)^2)/n-1

Question 5

Standard deviation (s)

Answer 5

s = sqrt(s^2)

Question 6

How to use your calculator to get:
a) Standard deviation
b) Variance
c) Mean

Answer 6

Make sure

Question 7

Interpreting the Standard Deviation s

Answer 7

a) The larger the standard deviation, the more spread out the data set is
b) s is affected by outliers
c) Best for bell-shaped and symmetric distributions

Question 8

Empirical rule for bell-shaped / symmetric distribution

Answer 8

68% of the observations within 1 stdv of the mean
95% of the observations within 2 stdv of the mean
99.7% of the observations within 3 stdv of the mean

Question 9

If the mean is equal to the median, which of the following is true?

Answer 9

The data is probably symmetric

Question 10

Distance from the data points to this measure of center always add up to zero

Answer 10

Mean