Answer Happy

Is smoking during pregnancy associated with more premature births? To investigate this question, researchers decide to examine pregnancy length (this is the variable.) They select a random sample of 114 pregnant women who were smokers. The average pregnancy length for this sample of smokers was 260 days. From a large body of research, it is known that length of human pregnancy has a standard deviation of 16 days. The researchers assume that smoking does not affect the variability in pregnancy length. 3/3 pts Question 1 The conditions are met for use of a normal model to represent the distribution of sample means. Which of the following are used to verify normality conditions for this scenario? the sample was randomly selected Correct. Whenever we calculate a confidence interval, we must have a random sample. Why? Because the margin of error and associated confidence level come from a normal probability model, and probability is based on random events. pregnancy length is normally distributed in the population of all pregnant smokers the sample size is greater than 30 Correct. For this scenario, we do not know if the variable (pregnancy length) is normally distributed in the population (pregnant smokers), but we don't care if the sample size is greater than 30.

5/5 pts Question 2 smokers, the researchers find a 95% confidence interval based on the To estimate the mean pregnancy length for the population of sample mean of 260 days. The standard error in the sample means is 1.5 days. The margin of error for the 95% confidence interval is 3 days. We are 95% confident that the mean pregnancy length for [Select] is between [Select] days and Select] days. Answer 1: 1.5 16 V114 Correct. The standard error for the sample means is va 1.50 Answer 2: 3 Good job. For a 95% confidence interval, the margin of error is 2 x SE (standard error): 2 16 ) 2 (1.50) = 3.0 Answer 3: the population of all pregnant smokers Good job.

Answer 4: 257 Good job. Here are our calculations: 260 2 (10) = 260 = 3 = 257 Answer 5: 263 Good job. Here are our calculations: 260 + 2 26 16 114 = 260 +3 = 263 2/2 pts Question 3 Which of the following is definitely in the 95% confidence interval? the observed sample mean Correct. The confidence interval is built around the observed sample mean. In fact, every confidence interval has the same form: sample statistic = margin of error the population mean