# 11.15 Refer to the data of Exercise 11.8a. Calculate a 95% confidence interval for ßb. What is the interpretation of Ho: B10 in Exercise 11.8?Noltems 1 1 1 1 2 2 22 23333Time4.8 14.7 13.79.52.4 11.8 10.5 12.0 14.3 16.4 17.9 14.5 16.7 20.1 16.8Noltems 33 333 4 4 44 4 4 4 4 45Time 20.8 26.8 12.9 13.0 15.4 10.8 20.3 22.3 20.0 21.9 20.7 20.9 19.9 17.1 19.1Noltems 5 5 5 5 6 6 6 6 6 6 6 777 7Time17.2 18.1 17.9 12.9 19.6 27.9 22.2 23.2 17.5 15.3 21.8 17.9 20.1 18.9 29.3Noltems 7 8 8 8 8 8 89 9 9 9 910 10 10Time 21.5 26.5 28.2 25.1 26.1 28.2 22.3 21.8 25.5 24.4 18.1 26.7 24.6 30.1 21.5Time 25.2 28.2 22.6 31.3 27.2 28.8 29.7 34.3 27.9 29.7 28.7 34.6 38.0 28.0 37.0Noltems 17 18 18 18 19 20 21 22 23 24 25 25 2526 27Time 32.5 39.5 39.0 37.0 35.5 38.3 44.0 39.6 42.3 34.6 44.9 47.4 49.2 45.8 44.0Noltems 27 30 30 31 37 39 40 41 45 46Time 46.1 42.9 48.3 46.0 48.2 54.7 49.9 55.4 57.1 52.4

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Step 1

a. Confidence interval:

The (1-α) % confidence interval for β1 is given by:

Step 2

Computing the 95% confidence interval for β1:

I have entered the data for treatments number of items, and time in rows 1 to 101 of columns A, and B respectively, with row 1 having the labels (Number of items and time).

The confidence interval is computed by using EXCEL. The software procedure is given below:

• Select Data > Data Analysis > Regression> OK.
• Enter Input Y Range as \$B\$1:\$B\$101 and Input x Range as \$A\$1:\$A\$21, tick on Labels, tick on confidence level and enter confidence level as 95%, enter output Range as \$D\$1 and click OK.

The outputs using EXCEL is as follows:

Step 3

Therefore, the 95% confidence interval for &beta...

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