Question

1- The average miles per gallon of (MPG) Light trucks produced by a company is 20 with a standard deviation of 3. The percentage of trucks with MPG less than 26 is?

2- The average cost per square meter for office rental space in the central business district of a large city is M = 235.80 with a standard deviation of 1.1. What z value is needed for the calculation of the 80% confidence interval.

Answer 1

Ans 1)

Mean

Population standard deviation = 3

Formula to calculate z-score:

ans.

Therefore,

The percentage of trucks with MPG less than 26 is 97.72%

/* we can calculate probability using excel function: =NORM.S.DIST(2,TRUE) */

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Ans 2)

Significance level: = 1 - 80/100 = 0.2

Z-value need for 80% confidence interval is:

z value is needed for the calculation of the 80% confidence interval: 1.282

/* we can finc value using excel function: =NORM.S.INV(0.2/2) = 1.282 */

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