. STA1510 MAYJUNE 2017 QUESTION 20 The mean life of a battery used in a digital
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STA1510 MAYJUNE 2017 QUESTION 20 The mean life of a battery used in a digital clock is 305 days The lives of the batteries follow a normal distribution The battery was recently modiied to last longer A sample of 20 of the modified batternes had a mean lfe of 311 days with a standard devation of 12 days A hypothesis test at 1% level of significance is undertaken to determine whether the modification increased the battery life The appropniate critical value of this test will be? 224 2 196 3 233 4 2 5395 5 2 8609 QUESTION 21 Refer to information given in question 20 what conclusion can be made about the battery lfe, given a l % level of sagraficance for the test? we do not reject the null hypothesis at the 1% level of significance and conclude that the mean battery life has increased 1 2 We reject the null hypothesis at the 1% level of significance and conclude that the mean battery life has not 3 We do not reject the null hypothesis at the 1% level of significance and conclude that the mean battery lfe 4 We reject the null hypothesis at the 1% level of significance and conclude that the mean banery life has 5 No conclusion can be made about the mean battery life as too lttle information is available increased has not increased increased TURN OVERExplanation / Answer
Critical value = 2.539
Hypothesis:
H0 : mu = 305
Ha : mu > 305
Test statistics:
t = (x -mean)/(s/sqrt(n))
= (311 - 305)/(12/sqrt(20))
= 2.2361
P value = .0187
Do not reject the null hypothesis
Correct answer is option 3)
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