Hypothesis testing is the foundation of conducting research in psychology. Researchers must first determine the question they wish to answer and then state their prediction in terms of null and alternative hypotheses. Once the hypotheses are stated, researchers move on to data collection. However, once the results come in, the real challenge is to determine if they have meaning, if the results are significant.
For example, a researcher asks whether attending a private secondary school leads to higher or lower performance on a test of social skills when compared to students attending publicly funded schools. After stating the hypotheses and collecting data, the researcher sees that the mean social skills scores for the two schools are different, but is the difference meaningful or just due to random variation? There must be a significant difference in order to say that the two schools really do have students with different social skills.
Scenario:
Imagine that the drug for severe depression from this week's Discussion was approved for use in humans. Researchers now want to know whether people using this drug have a different life expectancy than the rest of the general population. A sample of 100 patients who use the drug are followed over time. Those that use the drug have a mean life expectancy of 71.30 years. The mean life expectancy for the general population is 75.62 years. The population standard deviation is 28.
Assignment:
To complete this Assignment, submit by Day 7 responses to the following:
• Identify the independent and dependent variables.
• Explain whether the researcher should use a one-tailed or a two-tailed z test and why.
• State the null hypothesis in words (not formulas).
• State the alternative hypothesis in words (not formulas).
• Calculate the obtained z score by hand and state the critical value with an alpha of .05. Provide your calculations in your Assignment submission.
• Would you retain or reject the null hypothesis? Why?
• Explain whether the results are significant, and why or why not.
• What should the researcher conclude about the life expectancy of the sample in comparison to the population?
• In general, explain the relationship between z scores and the standard deviation.