Chapter 9

Question 1

standard deviation

Answer 1

one common way
to quantify
variation among
values.

Question 2

know the standard deviation formula

Answer 2

know the standard deviation formula

Question 3

range

Answer 3

the difference between the largest and smallest observations in a sample

Question 4

Standard deviation:

Answer 4

measures how far
observations tend
to be from the
mean.

Question 5

Why n – 1?

Answer 5

You could divide
by ‘n’ if you did
not intend to
extrapolate to the
true underlying
population.n-1 is the ‘best’ estimate of the SD of the entire
population based on a sample. i.e. it will lead to
accurate inferences when calculating C.I. and P-values.

Question 6

Situations in Which ‘n’ Can Seem Ambiguous

Answer 6

n must represent
the number of
independent
observations.
• Pseudoreplication
-counting
nonindependent.

Question 7

SD and Sample Size

Answer 7

.
• If sampling from
the same
population,
samples of
different sizes still
tend to have the
same SD.
• Note: SD has same
units as the mean.As you collect larger samples, you’ll quantify the
variability more precisely and more accurately,
but won’t change the variability.

Question 8

Variance

Answer 8

Equals the SD
squared.
• Expressed in the
same units as the
data but squared.
• Scientists
analyzing data do
not often report
variances.