Section outline

  • Topic 2

    Learning outcomes: Understand the properties of random samples selected from a population. Appreciate the role of sample size and variability in the distribution of possible sample outcomes. Recognize the importance of the normal distribution in statistics. 

    Calculate and interpret a confidence interval for the population mean; explain the difference between the standard deviation of a set of observations and the standard error of the mean; use the standard normal distribution to test hypotheses about a population mean; define the observed significance level.

    • Reflection on Biostatistics Topic 2 Forum
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      Please read “Chapter 2: Evaluating Results from Samples” in the course text (Basics of Biostatistics)

      Activity:

      We are asking each of you to manufacture twenty hypothetical patients and to "treat" them, assuming a cure rate of 50%.

      Firstly, determine whether each of the patients is "cured" using a procedure in which the probability of a "cure" is 50%.  Each patient should an equal chance of being cured or not cured.

      Count how many "cures" you have for the first 5 patients, the first 10 patients and then all 20 patients.

      Use GraphPad to calculate the confidence interval for each of the three groups of patients (first 5 patients, first 10 patients and all 20 patients). (www.graphpad.com/quickcalcs/confinterval2).

      Reflect on:

         1. How you randomly determined whether each of the hypothetical patients is cured or  not
         2. The 90%, the 95% and the 99% confidence interval for the true cure rate for each of the three groups
         3. Interpret the confidence intervals and explain why they are of different lengths
         4. Can you reject the null hypothesis that the true population cure rate is 50% based on any of your samples?