Reflection on Biostatistics Topic 3

Reading:

Chapter 4 (all) and Chapter 5 (up to page 115 only) in the e-book.

Activity

These are questions to check your understanding of the topic.

Answer any five of these questions.

Q1: A school principal wants to test if it is true what teachers say – that high school juniors use the computer an average 3.2 hours a day. What are our null and alternative hypotheses? 

Q2: Duracell manufactures batteries that the CEO claims will last an average of 300 hours under normal use. A researcher randomly selected 20 batteries from the production line and tested these batteries. The tested batteries had a mean life span of 270 hours with a standard deviation of 50 hours. Do we have enough evidence to suggest that the claim of an average lifetime of 300 hours is false? (HINT: A. state the null and alternative hypotheses; B. choose an appropriate statistical test; C. state the level of statistical significance and the conclusion)

Q3: If the difference between the hypothesized population mean and the mean of the sample is large, we ___ the null hypothesis. If the difference between the hypothesized population mean and the mean of the sample is small, we ___ the null hypothesis

Q4: At the Chrysler manufacturing plant, there is a part that is supposed to weigh precisely 19 pounds. The engineers take a sample of parts and want to know if they meet the weight specifications. What are our null and alternative hypotheses?

Q5: A group of students have an average SAT score of 1,020. From a random sample of 144 students we find the average SAT score to be 1,100 with a standard deviation of 144. We want to know if these high school students are representative of the overall population. What are our null and alternative hypotheses? 

Q6: A farmer is trying out a planting technique that he hopes will increase the yield on his pea plants. The average number of pods on one of his pea plants is 145 pods with a standard deviation of 100 pods. This year, after trying his new planting technique, he takes a random sample of his plants and finds the average number of pods to be 147. He wonders whether or not this is a statistically significant increase. What are his hypotheses and the test statistic? (HINT: A. First, we develop our null and alternative hypotheses; B. Next, we calculate the test statistic (use z-score) for the sample of pea plants.)