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A quality-control engineer records the lifetimes (in hours) of eight rechargeable batteries:
A battery is advertised as having a mean lifetime of 9.0 hours.
- [2]
Calculate the sample mean, xˉ, of the eight lifetimes.
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Calculate the unbiased estimate of the population standard deviation, sn−1.
At the 5% significance level, test whether the population mean lifetime is greater than 9.0h.
- [2]
Write down the null hypothesis H0 and the alternative hypothesis H1.
- [2]
Calculate the corresponding test statistic t.
- [1]
Determine the appropriate critical value for this test and state your conclusion in context.
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A tech reviewer measured the battery life (in hours) of 40 new-model laptops during a continuous video-playback test.
The cumulative-frequency graph below summarizes the results.
Use the graph to estimate:
- [1]
the median battery life.
- [2]
the inter-quartile range (IQR).
- [3]
Draw a box-and-whisker diagram to represent the battery life data. You may assume there are no outliers.
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