The table below shows the results from a drug trial for a new ADHD medication. Use the table to find the probability that a person's symptoms improved, given that they received the placebo and identify the type of probability found.
Table of contents
- 1. Introduction to Statistics53m
- 2. Describing Data with Tables and Graphs2h 2m
- 3. Describing Data Numerically2h 8m
- 4. Probability2h 26m
- 5. Binomial Distribution & Discrete Random Variables3h 28m
- 6. Normal Distribution & Continuous Random Variables2h 21m
- 7. Sampling Distributions & Confidence Intervals: Mean3h 37m
- Sampling Distribution of the Sample Mean and Central Limit Theorem19m
- Distribution of Sample Mean - ExcelBonus23m
- Introduction to Confidence Intervals22m
- Confidence Intervals for Population Mean1h 26m
- Determining the Minimum Sample Size Required12m
- Finding Probabilities and T Critical Values - ExcelBonus28m
- Confidence Intervals for Population Means - ExcelBonus25m
- 8. Sampling Distributions & Confidence Intervals: Proportion2h 20m
- 9. Hypothesis Testing for One Sample5h 15m
- Steps in Hypothesis Testing1h 13m
- Performing Hypothesis Tests: Means1h 1m
- Hypothesis Testing: Means - ExcelBonus42m
- Performing Hypothesis Tests: Proportions39m
- Hypothesis Testing: Proportions - ExcelBonus27m
- Performing Hypothesis Tests: Variance12m
- Critical Values and Rejection Regions29m
- Link Between Confidence Intervals and Hypothesis Testing12m
- Type I & Type II Errors16m
- 10. Hypothesis Testing for Two Samples5h 35m
- Two Proportions1h 12m
- Two Proportions Hypothesis Test - ExcelBonus28m
- Two Means - Unknown, Unequal Variance1h 2m
- Two Means - Unknown Variances Hypothesis Test - ExcelBonus12m
- Two Means - Unknown, Equal Variance15m
- Two Means - Unknown, Equal Variances Hypothesis Test - ExcelBonus9m
- Two Means - Known Variance12m
- Two Means - Sigma Known Hypothesis Test - ExcelBonus21m
- Two Means - Matched Pairs (Dependent Samples)42m
- Matched Pairs Hypothesis Test - ExcelBonus12m
- Two Variances and F Distribution29m
- Two Variances - Graphing CalculatorBonus15m
- 11. Correlation1h 24m
- 12. Regression3h 42m
- Linear Regression & Least Squares Method26m
- Residuals12m
- Coefficient of Determination12m
- Regression Line Equation and Coefficient of Determination - ExcelBonus8m
- Finding Residuals and Creating Residual Plots - ExcelBonus11m
- Inferences for Slope32m
- Enabling Data Analysis ToolpakBonus1m
- Regression Readout of the Data Analysis Toolpak - ExcelBonus21m
- Prediction Intervals13m
- Prediction Intervals - ExcelBonus19m
- Multiple Regression - ExcelBonus29m
- Quadratic Regression23m
- Quadratic Regression - ExcelBonus10m
- 13. Chi-Square Tests & Goodness of Fit2h 31m
- 14. ANOVA2h 32m
4. Probability
Introduction to Contingency Tables
Multiple Choice
The table below shows the results from a drug trial for a new ADHD medication. Use the table to find the probability that a person's symptoms didn't improve and they received the non-placebo and identify the type of probability found.

A
0.4; Joint probability
B
0.4; Conditional probability
C
0.2; Joint probability
D
0.2; Conditional probability
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Verified step by step guidance1
Step 1: Understand the problem. We are tasked with finding the probability that a person's symptoms didn't improve and they received the non-placebo. Additionally, we need to identify the type of probability being calculated (joint or conditional).
Step 2: Review the table. The table provides data on the number of people whose symptoms improved or didn't improve, categorized by whether they received the placebo or non-placebo. Specifically, the 'Not Improved' and 'Non-Placebo' intersection is 20.
Step 3: Calculate the joint probability. Joint probability refers to the probability of two events happening simultaneously. To calculate this, divide the number of people who didn't improve and received the non-placebo (20) by the total number of participants (100). The formula is:
Step 4: Understand conditional probability. Conditional probability refers to the probability of one event occurring given that another event has already occurred. If this were a conditional probability question, we would need to divide the number of people who didn't improve and received the non-placebo (20) by the total number of people who received the non-placebo (50). The formula would be:
Step 5: Identify the type of probability. Based on the problem, we are calculating the probability of two events happening simultaneously ('Not Improved' and 'Non-Placebo'), which is a joint probability.
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