Chapter·BiostatisticsPower and sample size

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1

A surgeon is interested in studying how different surgical techniques impact the healing of tendon injuries. In particular, he will compare 3 different types of suture repairs biomechanically in order to determine the maximum load before failure of the tendon 2 weeks after repair. He collects data on maximum load for 90 different repaired tendons from an animal model. Thirty tendons were repaired using each of the different suture techniques. Which of the following statistical measures is most appropriate for analyzing the results of this study?

AChi-squared

BWilcoxon rank sum

CPearson r coefficient

DStudent t-test

EANOVA

2

A researcher is conducting a study to compare fracture risk in male patients above the age of 65 who received annual DEXA screening to peers who did not receive screening. He conducts a randomized controlled trial in 900 patients, with half of participants assigned to each experimental group. The researcher ultimately finds similar rates of fractures in the two groups. He then notices that he had forgotten to include 400 patients in his analysis. Including the additional participants in his analysis would most likely affect the study's results in which of the following ways?

AWider confidence intervals of results

BIncreased probability of committing a type II error

CDecreased significance level of results

DIncreased external validity of results

EIncreased probability of rejecting the null hypothesis when it is truly false

3

An investigator is measuring the blood calcium level in a sample of female cross country runners and a control group of sedentary females. If she would like to compare the means of the two groups, which statistical test should she use?

AChi-square test

BLinear regression

Ct-test

DANOVA (Analysis of Variance)

EF-test

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