Biostatistics (I) Measuring Distributions & Calculating Probabilities

Question 1

What are the two main objectives of biostatistics?

Answer 1

1) To organize and summarize data (descriptive statistics) 2) To analyze samples of the data to reach conclusions (inferential statistics)

Question 2

What are the main types of biostatistical variable category?

(DC,QQ,R)

Answer 2

Discrete or continuous;

quantitative or qualitative,

random or not

Question 3

What symbol denotes population size?

(biostatistics)

Answer 3

N

Question 4

What symbol denotes sample size?

(biostatistics)

Answer 4

n

Question 5

What is the nominal scale?

(biostatistics)

Answer 5

A categorical organization of data into mutually exclusive and exhaustive subsets (e.g. male or female; child, adolescent, adult)

Question 6

What is the ordinal scale?

(biostatistics)

Answer 6

A scale of nominal categories that can be ranked

(e.g. low, medium, high)

Question 7

What is the interval scale?

(biostatistics)

Answer 7

A quantitative type of ordinal scale that ranks the nominal categories in equal portions

(e.g. 0 to 10, 10 to 20, 20 to 30)

Question 8

What are examples of the ratio scale?

(biostatistics)

Answer 8

Measurements of height, weight, and length

(there is a true zero and continuing ratios and intervals coming from that point)

Question 9

What type of sample should n be?

(biostatistics)

Answer 9

A simple random sample from the population N

Question 10

What symbol represents the population true mean?

(biostatistics)

Answer 10

Mu

Question 11

What symbol represents the sample mean?

(biostatistics)

Answer 11

X-bar

Question 12

How is population variance calculated?

Answer 12

σ​²

Question 13

How is population standard deviation calculated?

Answer 13

Take the square root of the pop. variance

(Square root of σ​²)

Question 14

How is sample variance calculated?

Answer 14

S²

Question 15

How is the sample standard deviation calculated?

Answer 15

S;

the square root of sample variance

(the square root of S²)

Question 16

How can a data set’s percentiles be found by hand?

Answer 16

50th percentile - find the median

25th percentile - find the median between the true median and the first data point

75th percentile - find the median between the true median and the last data point

Question 17

What equation can show us if a data point is an outlier?

Answer 17

Q1 - 1.5(IQR) to Q3 + 1.5(IQR)

Question 18

What equation allows for the calculation of probabilities in a binomial distribution?

What do the variables mean (p,n,x)?

Answer 18

p = probability of event in question

n = number of individuals in the group in question

x = probability of event occuring x times in the group

Question 19

Mutually exclusive events:

P(A and B) = ?

(Probability of both A and B occurring)

Answer 19

0;

the events are mutually exclusive

Question 20

To what is P(A’) equal?

(the probability of A not occurring)

Answer 20

1 - P(A)

(the inverse rule)

Question 21

How can the probability of events A or B be calculated?

(P(A or B) = ?)

Answer 21

P(A or B) = P(A) + P(B) - P(A and B)

Question 22

For two independent events, what is the probability of both event A and event B occurring?

Answer 22

P(A and B) = P(A) * P(B)

Question 23

How is the probability of event A calculated, given B?

(P(A|B) = ?)

Answer 23

P(A|B) = P(A and B) / P(B)