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How do you know if a ratio is high or low?
The ratios discussed so far are “high”—the difference between the numbers is large. The lowest possible ratio is one to one: one teacher to one student. If you are campaigning for more individual attention in the classroom, you want a higher number of teachers, but a lower student/teacher ratio.
Can you do a t test with percentages?
Thomas Hopkins , the issue isn’t that t-test isn’t appropriate for percentages. There are cases where t-test may be (more-or-less) appropriate for percentages. For example, if you had exam grades from each of your 2000 participants.
How to calculate Sample Size for comparing two proportions?
However, the effect of the FPC will be noticeable if one or both of the population sizes (N’s) is small relative to n in the formula above. To apply a finite population correction to the sample size calculation for comparing two proportions above, we can simply include f 1 = (N 1 -n)/ (N 1 -1) and f 2 = (N 2 -n)/ (N 2 -1) in the formula as follows.
When do you need to consider sample size?
If, one or both of the sample proportions are close to 0 or 1 then this approximation is not valid and you need to consider an alternative sample size calculation method. This is the minimum sample size for each group to detect whether the stated difference exists between the two proportions (with the required confidence level and power).
Which is larger the sample size or the power?
This reflects the confidence with which you would like to detect a significant difference between the two proportions. The higher the confidence level, the larger the sample size. The power is the probability of detecting a signficant difference when one exists. The higher the power, the larger the sample size.
How to estimate the proportions of two populations?
Since we don’t know the (assumed) common population proportion p any more than we know the proportions p 1 and p 2 of each population, we can estimate p using: the proportion of “successes” in the two samples combined. And, hence, our test statistic becomes: