Question

Graduate students in a statistics department recorded hours spent consulting on 21 different projects in a particular semester:

1	1	2	2	3	5	5	8	10	15	15
18	20	20	24	30	30	30	48	50	148

(a) Just by looking at the data values, how would we best describe the general appearance of a display (such as histogram or stemplot) of the data?

roughly normal

roughly symmetric but non-normal     

extreme skewness or outliers

somewhat skewed

(b) Use software to produce a 95% confidence interval for mean hours spent on a consulting project for all semesters, assuming this semester were typical. (Round your answers to two decimal places.)
(  ,  )

(c) Report the center of your confidence interval (sample mean). (Round your answer to two decimal places.)


Report the width of the interval. (Round your answer to two decimal places.)


(d) Delete the value "148" from the data set and produce a 95% confidence interval. (Round your answers to two decimal places.)
(  ,  )

(e) Report the center of your new confidence interval (sample mean). (Round your answer to two decimal places.)


Report the width of the new interval. (Round your answer to two decimal places.)


(f) Characterize the effects of the value 148 on the confidence interval.

equally dramatic effect on its center and its spread (width)

more dramatic effect on its center     

more dramatic effect on its spread (width)

Answer 1

1. THE BOXPLOT OF DATA LOOKS LIKE THIS

THE DATA IS ROUGHLY NORMAL.

(B) THE 95% CONFIDENCE INTERVAL IS GIVEN BY

MEAN = 23.1

S D = 32.08

3. THE SAMPLE MEAN IS GIVEN BY

4. NOW WHEN 148 IS REMOVED

MEAN = 16.85

SD = 14.88