Statistical Distribution

Question 1

epidemiology - Mean

Answer 1

Sum of values / total number of values

Question 2

epidemiology - Median

Answer 2

Middle value of a list of data sorted from least to greatest

Question 3

epidemiology - Median if there is an even number of values

Answer 3

The average of the middle 2 values

Question 4

epidemiology - Mode

Answer 4

MC value

Question 5

Measures of central tendency: Most affected by outliers (extreme values)?

Answer 5

Mean

Question 6

Least affected by outliers (extreme values)?

Mean mode or median?

Answer 6

Mode

Question 7

Measures of dispersion

Answer 7

1. Standard deviation

2. Standard error of the mean

Question 8

Standard deviation (SD or σ)

Answer 8

How much variability exists from the mean in a set of values

Question 9

Standard error of a mean (SEM)

Answer 9

An estimate of how much variability exists between the sample mean and the true population mean

Question 10

Standard deviation - standard error of the mean

Answer 10

SEM=σ/(n riza)

Question 11

Normal distribution

Answer 11

Gaussian or bell shaped

Mean=median=mode

Question 12

Normal distribution (proportion
1σ
2σ
3σ

Answer 12

68%
95%
99.7%

Question 13

Nonnormal distributions

Answer 13

1. Bimodal
2. Positive screw
3. Negative screw

Question 14

Bimodal distribution

Examples (3)

Answer 14

Suggest 2 different population 
Examples 
1. Age at onset of hodgkin
2. Suicide rate by age
3. Metabolic polymorphism such as fast vs slow acetylators

Question 15

Positive skew

Answer 15

Asymmetry with longer tail on right (peak at left)

Mean>median>mode

Question 16

Negative skew

Answer 16

Asymmetry with longer tail on left (peak on right)

Mean

Question 17

Measures of central tendency

Answer 17

1. Mean
2. Median
3. Mode

Question 18

statistical variance - definition and equation?

Answer 18

Variance is how far a set of numbers are spread out

variance = (standard deviation) in square

Question 19

how to decrease SEM (standard error of the mean)

Answer 19

increases n

Question 20

standard deviation vs precision

Answer 20

increased precision –> decreased standard deviation