Question

11. Using Excel - Scatter diagrams, estimated regression equations, and trendlines Suppose a company records data on sales calls, induding the length of each call and whether a sale was made. The manager is interested in determining whether there is a relationship between the average time spent per call and the number of sales made by each employee, so she obtains the average call length and the total number of sales over a 2-week period for a random sample of 30 employees. To answer the questions that follow, download an Excel@ spreadsheet containing the given data by dicking on the following words in bold: Download Excel File. The upper left-hand corner of the Excel spreadsheet in the file you download should look like the following sample spreadsheet. A 1 Employee B Average Length of Calls (Minutes) 2.3 C D Sales 50 2 3 2 5.4 57 4 3 1.1 41 5 4 3.2 54 O 5 54 7 6 1.4 38

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Answer 1

11.

Sales vs call length 70 60 50 40 30 20 y = 5.0799x + 32.094 R2 = 0.6424 10 0 0 1 N 3 4 5 6

A is appropriate chart.

The estimated regression equation is y = 5.0799x + 32.094. where y is the predicted value of the no. of sales for an employee and x is the value of the Average Call Length. The coefficient id determination is 0.6424 which means 64.24% variability in the no. of sales (y) can be explained using the estimated regression equation.

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13.

Since the sample size is large enough, you can assume that the sample mean x_bar follows normal distribtuion.

z = $\frac{\bar{x} - \mu}{\sigma/\sqrt{n}}$

A normal distribution with mean 0 and standard deviation 1.

test statistic: $\frac{18.1 -15.7 }{13.5/\sqrt{89}}$ = 1.677

14. Standard normal because we know population standard deviation

The P-Value is .401294.
The result is not significant at p < .05.

If you perform an upper-tailed test, p-value = 0.401. We fail to reject Ho in this case because the p-value is greater than significance level.

The P-Value is .802587.
The result is not significant at p < .05.

If you perform an two-tailed test, p-value = 0.802. We fail to reject Ho in this case because the p-value is greater than significance level.

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