Question

To inspect manufacturing processes, companies typically examine samples of parts for deficiencies. One company that manufactures ballpoint pens selected samples of pens on each of days. The company recorded, for each sample of , the number of defective pens in the sample. Here are their data:

1, 1, 2, 2, 2, 2, 3, 5, 5, 6, 6, 6, 9, 11, 14, 15, 18

Required:
a. Which measures of central tendency do not exist for this data set?
b. Which measures of central tendency would be affected by the change?
c. Which of the following best describes the distribution of the original data?
d. Suppose that, starting with the original data set, the largest measurement were removed. Which measures of central tendency would be changed from those of the original data set?

Answer 1

a. All measures exist

b. The Mean and the mode

c. Positively skewed

d. The mean and the median

Explanation:

a. The frequencies of the data are;

1 2

2 4

3 1

5 2

6 3

9 1

11 1

14 1

15 1

18 1

The formula for mode is given as follows;

The mean = 108/17 = 6.35

The median of 1 1 2 2 2 2 3 5 5 6 6 6 9 11 14 15 18 = (n + 1)/2th term = 9th term

∴ The median = 5

The mode = 3×Median - 2 × Mean = 15 - 2 × 6.35 = 2.29

Hence all exist

The answer is none theses measures

b. Whereby 18 is replaced by 39 the mean will be then be

(108 + 39 - 18)/17 = 7.59

The median, which is the 9th term remain the same;

Hence only the mean and mode will be affected

c. Since more values are concentrated on the left side of the data distribution, the distribution is positively skewed

d. The largest measurement = 18 the 17th term

Removal will give

Mean = (108 - 18)/16 = 5.625 Mean changes

Median = (16 + 1)/2 th term = 8.5th term = 5 The median remains the same

The mode = 3(Mean - Median) changes

Therefore, the mean and the median will be changed.