Chapter 7-8

Question 1

Compared to the mean, why is the median beneficial?

Answer 1

The median is not influenced by outliers

Question 2

The mode

Answer 2

is the value that occurs
most commonly; may not be useful
in noninteger continuous data if no
values occur more than once.

Question 3

Experimental

error:

Answer 3

imprecision
• Mistakes
• Natural variation
• Any kind of
variation not
explained by
treatments

Question 4

Recall that bias is

caused by

Answer 4

any
factor that
consistently alters
the results.

Question 5

Biased data are

not….

Answer 5

accurate

Question 6

Precise means

Answer 6

reproducible

Question 7

The 50th percentile is the

Answer 7

median

Question 8

The value of the 25th percentile subtracted from the

value of the 75th percentile is the

Answer 8

interquartile range

Question 9

Scatter plot: shows

Answer 9

every value More information
as long as not too
many
• Shows exactly how
the data are
distributed

Question 10

Box-and-whiskers plots

Answer 10

give
a sense of the distribution
of data without showing
every value.
• Good if too many values for
a scatter plot.

Question 11

‘Boxes’ usually represent

Answer 11

the 25th to 75th percentiles
(i.e. the interquartile
range) but can have
different meanings.

Question 12

Whiskers of then represent

Answer 12

5th and 95th percentiles,

but look carefully at figure descriptions.

Question 13

The cumulative
frequency
distribution compared to histogram

Answer 13

does not require bins; that the lines are artificially connecting the measuredvalues

Question 14

Any adjustment of
the data is a great
way to introduce bias.

Answer 14

• Eliminating “impossible”
values
• Accounting for biased
measurement opportunities
• Normalizing or
standardizing data
• Smoothing to make trends
more visible (e.g. rolling
average)
• Ok for graphs but never for
statistical calculations

Question 15

Interval Variables

Answer 15

• The difference of one
unit means the same
thing at all possible
values.
• e.g. degrees Celsius
• However, the meaning
of zero could be
arbitrary.• e.g. degrees Celsius
100°C is not twice as hot as 50°C.

Question 16

Ratio Variables

Answer 16

With a ratio variable,
zero is not arbitrary.
• e.g. height, weight
• It makes sense to
calculate ratios of
values.
• Degrees Kelvin is a
ratio variable because
0°K means no
temperature.
100°K is twice as hot as 50°K.

Question 17

Not Quite as Distinct as They Seem

Answer 17

• Many things can
be described with
more than one
type of variable.
• Example types:
• Continuous
• Interval
• Ordinal
• Discrete
• Binomial
• Nominal