Question

The hydrocarbon emissions at idling speed in parts per million (ppm) for automobiles of
1980 and 1990 model years are given for 20 randomly selected cars.
(a) For each model year, compute the sample mean, median, mode and midrange.
(b) For each model year, compute the variance and standard deviation of the data (to one decimal
digit).
(c) Comment on what the data indicate regarding whether or not the automobile emissions changed
from 1980 to 1990.

1980	1990
140	140
250	260
150	250
350	310
380	300
380	300
350	350
380	350
160	330
350	300

Answer 1

(a) For each model year, compute the sample mean, median, mode and midrange.
(b) For each model year, compute the variance and standard deviation of the data (to one decimal
digit).

Summary statistics for 1980

Summary statistics for 1990

(c) Comment on what the data indicate regarding whether or not the automobile emissions changed
from 1980 to 1990.

Hypothesis testing to check if the automobile emissions changed from 1980 to 1990.

Let sample 1 be 1980
Let sample 2 be 1990

Hence we do not have sufficient evidence to claim that the the automobile emissions changed from 1980 to 1990 significantly.