Use the normal approximation to the binomial to find the following probabilities

Question

Use the normal approximation to the binomial to find the following probabilities. Seventy percent of people in the U.S. have type O blood. You randomly select 30 people in the U.S. and ask them if they have type O blood. Are np and nq both greater than 5? np = _____ nq = _____ mean = _____ st. dev. = _____ a) Exactly 20 people have type O blood b) At least 20 have type O blood c) Fewer than 20 have type O blood You took a random sample of 13 two-slice toasters and found the mean price was $ 61.12 and the standard deviation was $ 24.62. Assume the prices are normally distributed. Find a 90% confidence interval for the population mean. Is this a z-dist, t-dist, or neither, and why? _____ Critical value from table _____ Margin of Error _____ Confidence interval _____

Explanation / Answer

12)

This is a t test because sample size is less than 30

Critical value from table = +/-1.78

Margin of error = critical value * s / sqrt(n)

= 1.78 * 24.62 / sqrt(13) = 12.15

Confidence interval = mean + / - t * s / sqrt(n)

= 61.12 + / - 1.78 * 24.62 / sqrt(13)

= (48.97 , 73.27)

48 .97 <mu < 73.27

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