How Reliable Is Reliable

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156 184 176 183 174

184 166 159 169 178

The engineer conjectured that the average Brinell hardness of all such ductile iron pieces is greater than 170. Do you support the engineer’s hypothesis? What will be the 95% confidence interval in that context?

2. A manufacturer claims that the thickness of the spearmint gum it produces is 7.5 one-hundredths of an inch. A quality control specialist regularly checks this claim. On one production run, he took a random sample of n = 10 pieces of gum and measured their thickness. He obtained the following. What will be his conclusion?

7.63 7.64 7.67 7.66 7.54

7.55 7.40 7.48 7.53 7.56

3. The first row is the miles per gallon for U.S. cars and the second row is miles per gallon for Japanese cars.

18 15 18 16 17 15 14 14 14 15 15 14 15 14 22 18 21 21 10

24 27 26 25 30 32 23 17 28 23 27 20 22 17 20 31 32 31 32

Test whether the Japanese cars provide at least 10 miles/gallon extra mileage on an average.

Assignment-3

1. Many users of mobile phone prefer to recharge their mobile through online transactions. A mobile service provider recorded following transactions (in rupees) for mobile phone top-up recharge during a certain time interval:

108,104,106,89,89,127,109,89,111,82,100,121,87,106,130,64,103,118,

96,96,85,115,101,37,69,125,102,86,119,91,103,88,146,115,90,115,

78,93,104,66,83,94,106,101,82,160,106,102,91,105,95,105,119,106,

42,117,100,88,107,75,91,114,91,112,89,96,52,90,129,86,93,101,

87,99,118,81,113,119,85,64,86,105,103,140,80,97,69,81,105,128,

94,57,99,80,89,82,122,116,73,122,451,321,535,446,537,392,497,390,

452,573,498,603,439,300,530,520,388,592,589,559,441,446,513,718,410

Summarize the data.

2. Consider the following data:

x (year) 2012 2013 2014 2015 2016

y (sales) 12 19 29 37 45

a) Find the least square regression line y = ax + b.

b) Use the least squares regression line as a model to estimate the sales of the company in 2017.