Valparaiso University Contingency Table for Two Categorical Variables Worksheet

Use the data I provide in Exel to answer the questions! I would prefer that you use number of bedrooms & whether they have a toilet as categorial items.

1. Use your “sample” from Dollar Street from the previous activity (or collect new data). Use the graphs and questions from the last activities to inspire your investigation. You can be inspired by ideas of your classmates, too. Due to sample size limitations of Dollar Street, you can take a census from Dollar Street and consider this your sample of people from the world. Take as large of sample as you can, or 30 families. Talk to your instructor if you have any thoughts/concerns.
2. Construct at least one contingency table for two categorical variables.
3. Construct at least 1 confidence interval:
   1. Inference for 1 population proportion: confidence interval
      1. You’ll need a categorical variable to work with. Of the outcomes for the variable, YOU decide what the success will be (e.g. “yes” is a success). Compute the point estimate.
      2. Check the conditions for a confidence interval. Show that the conditions are met or not met by carefully checking each condition. But….move forward anyway if the conditions aren’t met. 🙂
      3. Compute a 95% confidence interval for the point estimate.
      4. Correctly interpret the confidence interval in a sentence. (See textbook for help on this.)
   2. Need inspiration?
      • Compare the proportion of __________ between two countries/continents.
      • Compare the proportion of __________ between the upper quartile of families income for two different countries/continents.
      • Find a statistics online: For example, if you know that (say) 55% of American families own a dog, does the percent of families that own a dog in your sample disagree with 55%? Aim for reputable sources when you look for a percentage for the null hypothesis. If you have a question about a reputable source, you can ask your instructor.
4. In 1-2 paragraphs, describe what the data are telling you. What do you observe about the families in this data set? What comparisons between groups can you make?
5. Follow the writing guidelines:
   • In general, round decimals to two places. Values in the same paragraph or table should have the same number of decimal places.
   • Don’t state formulas for common statistics (e.g. variance, z score) in your paragraphs.
   • If the decimal is less than one:
     • Place a zero before the decimal point if the statistic can be greater than one (e.g. 0.26 lb).
     • If number cannot be greater than one, leave out the decimal point (e.g. p = .015).
   • Most symbols and abbreviations that are not Greek letters are italicized: p N n z SD SE M. All symbols should be italicized: t, F, z. It’s ok to use M to represent the mean, SD for standard deviation, SE for standard error, N for sample size, n for fraction of a sample.
     • Use an uppercase N for number in the total sample (N = 96) and a lowercase n for a fraction of the sample (n = 49).
   • Place percentages in parentheses when you’ve estimated the percentage in words. For example: “Almost a quarter of the sample (25.5%) was already infected with the bacteria.”
   • Confidence intervals: For CIs, use brackets: 95% CI [2.47, 2.99], [-5.1, 1.56], and [-3.43, 2.89]. If you are reporting a list of statistics within parentheses, you do not need to use brackets within the parentheses. For example (SD = 1.5, CI = -5, 5)