Q1. The weights of first graders at Freemont Elementary were recorded as follows. Construct a frequency distribution (including cumulative frequency) using 6 classes and starting with 45.
45 50 60 65 62 57 62 65
49 46 50 51 58 62 67 71
Q2. Find the range and variance of the following data set:
45, 51, 53, 76
Q3. A.C. Neilson reported that children between the ages of 4 and 9 watch an average of 22 hours of TV per week. Assume the variable is normally distributed and the standard deviation is 4 hours. find the probability that a randomly selected child will watch fewer than 18 hours of TV.
Q4. The average teacher's salary in Arizona is $42,300 with standard deviation $5000. Assuming a normal distribution, what is the probability that the mean of a sample of 50 teachers' salaries will be at least $48,000 a year?
Q5. If a baseball player's batting average is 0.275, find the probability that the player will get at least 40 hits in 100 times at bat.
Q6. Thirty randomly selected vehicles were stopped, and the tread depth of the right front tire was measured. The mean was 0.20 inch, and the standard deviation was 0.05 inch. Find the 95% confidence interval of the mean depth. Assume the variable is approximately normally distributed.
Q7. A statistics instructor is asked to estimate the average age of students at the college at 99% confidence with accuracy within 2 years. A previous study determined that the standard deviation was 5 years. How large a sample is needed?
Q8. In a recent study of 250 female freshmen showed that 70 did not want to work after marriage. Find the 95% confidence interval of the true proportion.
Q9. Find the 99% confidence interval for the variance and standard deviation for the lifetime of batteries if a sample of 40 has a standard deviation of 3.4 months. Assume the variable is normally distributed.
Q10. A researcher wishes to test the claim that the average age of lifeguards is greater than 22 years. The researcher sampled 56 lifeguards and found an average of 23.7 years with a standard deviation of 2 years. Test the claim at "alpha" = 0.05.