Statistics: Comparing 2 proportions Flashcards

1
Q

What is meant by independent samples?

A

The observations in one sample are independent of those in another sample.

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2
Q

When are two samples dependent?

A

When they have the same subjects, if they’re in matched pairs (each subject in one sample is matched with a subject in the other sample,) or when each sample is observed twice.

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3
Q

What is a meta analysis?

A

Combines the results of several studies that address a set of statistical questions.

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4
Q

When is the sampling distribution normal?

A

When it has a large sample

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5
Q

What do negative signs mean in a confidence interval

A

P1 is less than P2 by that variable.

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6
Q

What does it mean if the confidence interval contains 0?

A

There’s insufficient evidence to infer whether p1 or p2 is larger

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7
Q

What is the format for a null hypothesis when comparing two groups?

A

H0: (p1- p2)=0

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8
Q

What is meant by a pooled estimate

A

one that pools the total number of successes and total number of observations from the two samples in the format s1+s2/n1+n2 where s= successes.

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9
Q

What does the test statistic measure?

A

the number of errors that the sample estimate falls from its null hypothesis

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10
Q

What are the assumptions for a two sided confidence test for comparing two population proportions

A

Categorical for both groups, Independent random samples, five successes and failures in n1 and n2 if using two sided alternative

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11
Q

What is the format for a one sided alternative hypothesis?

A

H0: (p1-p2) >/< 0

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12
Q

If we’re comparing two proportions then the standard error of the difference is ________ than the standard error for either sample portion alone

A

Larger

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13
Q

How do you estimate the df in the confidence interval between two population means

A

The smaller of (N1-1) and (N2-1)

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14
Q

When can we not rely on the central limit theorem

A

When the sample size is under 30

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15
Q

What assumptions are there in a confidence interval for the difference between two population means ?

A

Independent random samples and an approximately normal dist. in each group.

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16
Q

List three possible interpretations of the confidence interval

A

If 0 falls in the interval it means M1=M2 is possible.
If it only contains positive numbers then it suggests that M1-M2 is positive therefore we infer that M1 is larger than M2
If it only contains negative numbers then it suggests that M1-M2 is negative therefore we infer that M1 is smaller than M2

17
Q

When are one sided t tests not trustworthy?

A

When the sample size is under 30 and the distribution is skewed.

18
Q

What is meant by the pooled standard deviation?

A

The combination of information from the two samples to provide a single estimate of variability.

19
Q

What is meant by the relative risk?

A

The ratio of proportions (p1/p2) in medical applications for which the proportions refers to an outcome which i undesirable, such as death or having a heart attack.

20
Q

What are the assumptions of a paired difference t test?

A

The sample of difference scores is a random sample from a population of difference scores and they have an approximately normal distribution.