Statistical concepts I Flashcards Preview

Quiz 3 biostatistics > Statistical concepts I > Flashcards

Flashcards in Statistical concepts I Deck (17)
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1
Q

when would you use a chi-squared statistic?

A

Compares observed cell frequences (ex: of a 2x2 table) with expected frequencies

2
Q

Chi-squared formula

A

Sum of (O-E)^2/E

3
Q

When is a chi-squared stat significant?

A

If it is >3.84

4
Q

how do you determine how many degrees of freedom to use with a chi-squared statistic?

A

(r-1)x(c-1)

5
Q

What is the formula for odds ratio?

A

p1/(1-P1) / p2/(1-p2)

6
Q

When do you use a t test?

A

To compare the means between two groups

7
Q

When do you use logistic regression?

A

When there are more than 2 binary variables

8
Q

how do you calculate the t statistic?

A

Take the difference (P2-P1) and divide by the standard error of the difference

9
Q

What sample size must you have for the standard t statistic calculation to work?

A

N>50

10
Q

What do you do with a t statistic if you have n<50?

A

the data must follow a normal distribution to work. Also, some changes in the formula

11
Q

when do you use paired samples t test?

A

Comparison of pre and post study results (i.e. before vs after)

12
Q

What is the required sample size for a paired t test?

A

100

13
Q

when do you use one-way analysis of variance?

A

To compare more than 2 groups

14
Q

what is the survival function?

A

probability that an individual will survive beyond time t

15
Q

What is the survival curve?

A

Graph of the survival function

16
Q

What is the hazard estimate?

A

Probability of dying in a given time interval

17
Q

What stat test do you use for estimating survival curves?

A

log-rank test