# The control limits for an x-bar chart are how many standard deviations above and below the process mean?

Which of the following is not a characteristic of the normal probability distribution? Answer The graph of the curve is the shape of a rectangle The total area under the curve is always equal to 1. 99.72% of the time the random variable assumes a value within plus or minus three standard deviations of its mean The mean is equal to the median, which is also equal to the mode. Question 2 A manufacturer wants to estimate the proportion of defective items that are produced by a certain machine. A random sample of 50 items is taken. Which Excel function would not be appropriate to construct a confidence interval estimate? Answer (I feel this question is a bit ambiguous. The answer depends upon in what form data is given. I have chosen the best answer) NORMSINV COUNTIF STDEV All are appropriate. Question 3 The expected value of the random variable is Answer s the standard error the sample size the population mean Question 4 Ordinary arithmetic operations are meaningful Answer only with categorical data only with quantitative data either with quantitative or categorical data with rank data Question 5 It is known that the population variance equals 484. With a 0.95 probability, the sample size that needs to be taken to estimate the population mean if the desired margin of error is 5 or less is Answer 25 74 189 75 Question 6 In a sample of 800 students in a university, 160, or 20%, are Business majors. Based on the above information, the school’s paper reported that “20% of all the students at the university are Business majors.” This report is an example of Answer a sample a population statistical inference descriptive statistics Question 7 The control limits for an x-bar chart are how many standard deviations above and below the process mean? Answer one two three four