Look at the picture, which one is the correct answer?

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Sales at a fast-food restaurant average $6,000 per day. the restaurant decided to introduce an advertising campaign to increase daily sales. to determine the effectiveness of the advertising campaign, a sample of 49 days of sales were taken. they found that the average daily sales were $6,300 per day. from past history, the restaurant knew that its population standard deviation is about $1,000. if the level of significance is 0.01, have sales increased as a result of the advertising campaign? multiple choicea)fail to reject the null hypothesis. b)reject the null hypothesis and conclude the mean is higher than $6,000 per day. c)reject the null hypothesis and conclude the mean is lower than $6,000 per day. d)reject the null hypothesis and conclude that the mean is equal to $6,000 per day. expert answer

Industrial engineers who specialize in ergonomics are concerned with designing workspace and devices operated by workers so as to achieve high productivity and comfort. a paper published in this research area reports on a study of preferred height for an experimental keyboard with large forearm-wrist support. a sample of 31 trained typists resulted in an average preferred height of 80.0 cm