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NBME 22 Answers

nbme22/Block 3/Question#22

A study is conducted to assess the prevalence of ...

Chi-square test

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submitted by usmleuser007(131),

Just remember:

1) T-test (tea for two) = looks at the mean values of 2 groups

2) ANOVA (analysis of variance) ~ like t-test but = looks at mean values of 3 or more groups

3) Chi-square = looks at the (%) or proportions between 2 or more groups.

so, just look for how many groups being addressed and what values they are using (% or means)

 +9  upvote downvote
submitted by mcl(223),

Despite a numeric value (blood pressure) being measured, patients would be designated either hypertensive or normotensive. To my understanding, the best test for comparing categorical variables across groups is a chi square test.

In contrast, a t-test is used to compare between the means of two groups (measured variable must be quantitative).

 +2  upvote downvote
submitted by d_holles(39),

I was never taught what t-test vs Chi-squared was. Going off of the FA table didn't help. This video below explained the concept really well.


For the Q refer to @mc1's comment.

1) Analysis of variance is a procedure used for comparing sample means to see if there is sufficient evidence to infer that the means of the corresponding population distributions also differ.

2) Where t-test compare only two distributions, analysis of variance is able to compare many. • What does the one-way part mean? It is one dependent variable (always continuous) and exactly one independent variable (always categorical). A single independent variable can have many levels.

drdoom  via @usmleuser007 https://www.slideshare.net/adsarwar/anova-and-ttest +  

Why is the correct answer chi-square test? I get that it’s used for categorical variables but we’re comparing prevalence percentages. Is that considered categorical?

liverdietrying  You’re looking at two categorical variables, Caucasian vs. AA and HTN versus normotensive. So you’re still using Chi2 to analyze. +1