# statistics

posted by .

A hypothetical HIV vaccine trial involving 20,000 participants—10,000 in the vaccine group and 10,000 in the placebo group—had the following results: 6.3 infections per 1000 in the vaccine group and 9.0 infections per 1000 in the placebo group.

I ran a computer simulation to predict possible outcomes of the trial if the null hypothesis is true—that is, if vaccinated and unvaccinated people are equally likely to contract HIV. I ran 1000 virtual trials of 20,000 people (10,000 per group) assuming that the vaccine is ineffective. Outcomes are expressed as excess infections in the placebo group. Here are the results of the 1000 virtual trials displayed as a histogram.

1. Roughly estimate the (two-sided) p-value associated with the trial’s outcome from the histogram.

2. From the simulation, I learn that the statistic ‘excess infections in the placebo group’ follows a normal distribution with a mean of 0 and a standard deviation (standard error) of 12.3. Use this information to calculate the two-sided p-value more precisely than in (11). Round to the nearest thousandth.

4. The effect size in this hypothetical trial (2.7 fewer infections per 1000 vaccinated) is slightly smaller than the effect size found in the real 2009 HIV vaccine trial (2.8 fewer infections per 1000 vaccinated); so why is the p-value smaller?

A) The hypothetical trial has less variability.
B) The sample size of the hypothetical trial is larger.
C) The real trial did not follow a normal distribution.
D) The real trial used an intention to treat analysis.

• statistics -

lk

• statistics -

Can some one help us to answer this question

## Similar Questions

1. ### Epidemiology

Indicate how the bias would affect the measure of association. Would it be under estimated, or over estimated or unchanged. Persons diagnosed as HIV positive or negative were interviewed about their number of lifetime sexual partners. …
2. ### Economics - Cost benefit analysis

Imagine that there are two cohorts of 100 patients each. One group got the flu vaccine and other group did not. Outcomes Vaccine Group Outcomes = 90 patients without the flu No-Vaccine Group Outcomes = 50 without the flu Costs Vaccine …
3. ### statistics

A group of adults of 200 aged 21 to 50 were selected from those entering Fit Right Health stores in Washington state, and were randomly divided into two groups. One group was given an herb and the othe placebo. After 6 months, the …
4. ### statistics

Surgery vs. placebo for the knee pain: Refer to Example 10. Is Arthroscopic Surgery Better than Placebo?
5. ### Psychology

A psychologist is performing an experiment involving a controlled group and an experimental group. With the experimental group, the psychologist is giving a placebo and labeling it as caffeine pill. The control group receives a caffeine …
6. ### Can someone help with this?

A psychologist is performing an experiment involving a controlled group and an experimental group. With the experimental group, the psychologist is giving a placebo and labeling it as caffeine pill. The control group receives a caffeine …
7. ### Statistics

The effect size in this hypothetical trial (2.7 fewer infections per 1000 vaccinated) is slightly smaller than the effect size found in the real 2009 HIV vaccine trial (2.8 fewer infections per 1000 vaccinated); so why is the p-value …
8. ### Psychology

What is the independent and dependent variable in this scenario: A Physiological Psychologist is interested in investigating the effects of a new anti-anxiety drug on maze running behaviour in rats. A pool of rats is divided into two …
9. ### statisticsbob

Perform a one-way ANOVA analysis, testing at the 0.05 level. Also, calculate the mean number of sick days for each group. Describe your results. But equally important, also explain what you would do if you owned your own company. Would …
10. ### math

Several studies have been conduct on the effectiveness and safety of the H1N1 influenza vaccine. One study found that in a group that received the actual medication, the drug was 87% effective. In a group that received a placebo, there …

More Similar Questions