Confidence intervals, p-values + hypothesis testing

Question 1

What is the standard deviation?

Answer 1

Describes variability of observations in the sample

Question 2

What is the standard error

Answer 2

Measure of the precision of an estimate of the population paramter

Question 3

What is variance?

Answer 3

The value of deviation from the mean

Question 4

How is variance calculated?

Answer 4

(Σ(x−x(bar))^2)/(n−1)

The sum of the difference between values and the mean, squared, divided by n-1

Question 5

How is standard deviation calculated?

Answer 5

Square root of variance

Question 6

How is standard error of the mean calculated?

Answer 6

SD/√n

Standard deviation/root of sample size

Question 7

How is standard error of a proportion calculated?

Answer 7

√(p(1-p))/n

Root of proportion divided by sample size

Question 8

How is standard error of difference between two sample means calculated?

Answer 8

Used to compare two independent samples
√(SD^2/n)+(SD^2/n)
Sample standard deviation squared/sample size aded together

Question 9

How is standard error of the difference between two proportions calculated?

Answer 9

√(proportion 1)+(proportion 2)

Proportion = p(1-p)/n

Question 10

How is the 95% confidence interval calculated for the mean?

Answer 10

x(bar)+/-[1.96xSE(mean)]

Question 11

How is the 95% confidence interval of a proportion calculated?

Answer 11

p+/-[1.96xSE(proportion)]

Question 12

How is the 95% confidence interval calculated for the difference in two means?

Answer 12

x(bar1)-x(bar2)+/-[1.96xSE(difference in means)]

Question 13

How is the 95% confidence interval calculated for the difference in two proportions?

Answer 13

p1-p2+/-[1.96xSE(difference in proportions)]

Question 14

What does the p value tell us?

Answer 14

The probability of obtaining these results, or more extreme, when the null hypothesis is true

Question 15

What is a type I error?

Answer 15

False positive
Rejecting the null hypothesis when it is true
Given as α

Question 16

What is a type II error?

Answer 16

False negative
Not rejecting the null hypothesis when it is actually false
Given as β

Question 17

What is the power?

Answer 17

Probability of rejecting the null hypothesis when it is actually false

Question 18

How is power calculated?

Answer 18

1-β

Question 19

What does a 95% confidence interval for a mean show us?

Answer 19

If the study were repeated 100 times, of the resulting 100 CI for the mean, we would expect 95 of these to include the true population mean
It is a range of values which will include the true population mean for 95% of possible samples

Question 20

How is the test statistic (Z) calculated?

Answer 20

(Observed value-hypothesised value)/Standard error of observed value
Usually hypothesised value = 0