Directions (read before starting)
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This lab focuses on developing a conceptual understanding of hypothesis testing using the randomization approaches implemented by StatKey.
On this lab, when performing a hypothesis test you should include each of the following steps:
Shown below is an example of what a good answer would look like for these 3 steps involving the Johns Hopkins premature birth survival rate example. Recall that the claim being tested is Wikipedia’s statement that the survival rate of babies borth at 25 weeks gestation is 70% and the observed sample data contained 31 of 39 babies born at this age surviving.
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In this section you will analyze data from 3 different studies. When asked to perform a hypothesis test please make sure you follow the steps described in the Introduction in order to receive full credit.
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To assess whether oatbran cereal might be effective in reducing LDL cholesterol, researchers randomly assigned 14 adult males with high cholesterol into two groups:
We’ll analyze each subject’s difference in LDL cholesterol when they were on the oatbran diet relative to when they were on the cornflakes diet. This outcome is recorded as the variable “difference” in the dataset linked below. You should recognize that a positive value of “difference” indicates a reduction in LDL cholesterol when on the oatbran diet.
Question #1:
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The impacts of recreational drugs, including cannabis, on driving have been an active area of research over the past several decades. Because it would be unethical to place drug-impaired drivers onto real roadways, these studies are typically done using advanced driving simulators like the one below:
One study conducted using the NADS-1 driving simulator involved 19 volunteer participants who each engaged in 45-minute simulated drives under 6 different dosing conditions:
These conditions were randomly assigned across the participant’s 6 visits, and were separated by washout periods of at least 10 days. The alcohol dosing condition involved the participant drinking either fruit juice mixed with 90% grain alcohol until their breath alcohol concentration (BrAC) was 5%, or drinking a placebo drink that consisted of fruit juice with an alcohol-swabbed rim for a comparable amount of time. The cannabis dosing condition occurred after alcohol dosing, and had the participant inhale placebo, low THC, or high THC cannabis ad-libitum (at their own pace) from a vaporizer for 10-minutes.
One of this study’s research questions was whether each participant’s lateral control (lane-keeping ability) worsened after drug use. The researchers measured this using standard deviation of lateral position (SDLP), which roughly corresponds with the average deviation from the center of the lane. Thus, higher SDLP values indicate more variability in lane position and thus correspond to worse lateral control (more side-to-side movement within the lane).
The table below displays SDLP (in cm) for each subject under the Placebo-Placebo condition during an interstate segment of the drive. The additional columns of the table display whether a participant’s SDLP increased for the other dosing conditions (relative to the control condition of Placebo-Placebo). A value of “1” indicates higher SDLP compared to their placebo-placebo drive.
| Participant | Baseline SDLP | Placebo/Low THC | Placebo/High THC | Alcohol/Placebo | Alcohol/Low THC | Alcohol/High THC |
|---|---|---|---|---|---|---|
| 1 | 14.2 | 0 | 0 | 1 | 1 | 1 |
| 2 | 17.9 | 0 | 1 | 1 | 1 | 0 |
| 3 | 19.9 | 1 | 0 | 1 | 1 | 0 |
| 4 | 11.4 | 0 | 0 | 1 | 1 | 1 |
| 5 | 18.3 | 1 | 1 | 0 | 0 | 1 |
| 6 | 18.5 | 0 | 1 | 1 | 1 | 0 |
| 7 | 15.8 | 1 | 1 | 1 | 1 | 1 |
| 8 | 15.9 | 1 | 1 | 1 | 1 | 0 |
| 9 | 15.8 | 0 | 0 | 1 | 1 | 0 |
| 10 | 15 | 1 | 1 | 0 | 1 | 0 |
| 11 | 16 | 1 | 1 | 1 | 1 | 1 |
| 12 | 14.7 | 0 | 1 | 1 | 1 | 1 |
| 13 | 15.3 | 1 | 1 | 1 | 1 | 1 |
| 14 | 17.4 | 1 | 1 | 0 | 1 | 1 |
| 15 | 19.6 | 0 | 0 | 1 | 1 | 1 |
| 16 | 16.9 | 1 | 1 | 0 | 0 | 1 |
| 17 | 15.9 | 1 | 0 | 1 | 1 | 0 |
| 18 | 14.9 | 1 | 1 | 1 | 0 | 1 |
| 19 | 15.1 | 1 | 1 | 1 | 1 | 1 |
| Total | 12 | 13 | 15 | 16 | 12 |
Question #2: If a dosing condition has no impact on driving performance, you’d expect it to be equally likely for an individual to have a higher or a lower SLDP on their dosed drive relative to their placebo drive. Keep this in mind when responding to the following questions.