A manufacturer of cordless electric shavers sampled 13 from a day\'s production

Question

A manufacturer of cordless electric shavers sampled 13 from a day's production and found the mean time of continuous usage without recharging to be 410 minutes with a sample standard deviation of 30 minutes. We can assume that times are normally distributed. We wish to test if the true mean operating time without recharging is more than 400 minutes.

The correct null and alternative hypotheses are
Question 1 options:
A) H0: µ = 400; HA: µ ? 400
B) H0: µ < 400; HA: µ= 400
C) H0: µ = 400; HA: µ > 400
D) H0: µ = 400; HA: µ < 400
E) H0: µ > 400; HA: µ= 400

Explanation / Answer

The correct answer is C. The null hypothesis is always = to something the alternate will either be or is not equal to. In the last sentence it says "mean operating time without recharging is MORE THAN 400 minutes" that is where you get the > sign

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