Biostats

Question 1

Stratum Sample Size with Proportional Allocation

Answer 1

Stratum Sample Size = (Total Sample Size x Stratum Size) / Population Size

Question 2

Type of distribution where the “tail” elongates to the LEFT

Answer 2

Negatively/Left Skewed (mean < median)

Question 3

Type of distribution where the “tail” elongates to the RIGHT

Answer 3

Positively/Right Skewed (mean > median)

Question 4

Which measure of center is affected by outliers – mean or median?

Answer 4

Mean

Question 5

Sample Standard Deviation, s

Answer 5

Algebra steps:

sum the squares of the data values (x)

find the square of the sum of the data and divide by n

subtract to find the numerator

divide by n-1

take square root

*Note: to find the sample variance, just eliminate the square root part

Question 6

What percentage of observations lie within one SD of either side of the mean?

Two SD?

Three SD?

Answer 6

68%, 95%, 99.7%

Question 7

Lower Limit?

Upper Limit?

Answer 7

Lower Limit = Q1 - (1.5*IQR)

Upper Limit = Q3 + (1.5*IQR)

Question 8

Population Mean?

Answer 8

Question 9

Population Standard Deviation

Answer 9

Algebra Steps:

sum the squares of the data values (x)

divide by N

subtract the square of the mean

take the square root

*Note: to find the population variance, just eliminate the square root part

Question 10

Z-score

Answer 10