Question

Consider the following data set of skid distance in feet): 12, 17, 8, 9, 11, 5, 22, 17, 11, 16, 17, 15, 20 sa continuation of number 7. Use your work from above. Suppose that the skid distances In what interval would you expect to find 68% of the skid data? 518, 11, 11, 12, 15, 17, 17,17 18,19,20,22 17 a. Sample size: 13 c. Range: b. Mode: d. Mean: 14.8 e. Median: 17 Drmally distributed with a standard deviation of 4 feet. In what interval would you expect to find 95% of the skid data? is a skid distance of 20 feet considered unusual? etermine the z-score for a skid distance of 10 feet.

Answer 1

(7)

(a)

Sample size = n = 13

(b)

Mode = 17

since 17 occurs maximum number of times

(c)

Range = Maximum - Minimum = 22 - 5 = 17

(d)

Mean () is given by:

T

192 = 14.8 13

(8)

(i)

68% of data lie within Mean - SD and Mean + SD

i.e., 14.8 - 4 and 14.8 + 4

i.e.   10.8 and 18.8

So,

Answer is:

10.8 and 18.8

(ii)

95% of data lie within Mean - 2 SD and Mean + 2 SD

i.e., 14.8 - (2 X 4) and 14.8 + (2 X 4)

i.e.   6.8 and 22.8

So,

Answer is:

6.8 and 22.8

(iii)

For X = 20:

Z = (20 - 14.8)/4

= 1.3 < 2

Since Z is less than 2, we conclude:

a skid distance of 20 feet is not unusual.

(iv)

For X = 10:

Z = (10 - 14.8)/4

= - 1.2

Answer is:

- 1.2