3. Basic Statistics I

Question 1

Why are central tendency measures useful in vet med?

Answer 1

Help you understand and critically evaluate the medical research literature

Understand patients values in relations to larger population

Understand biological variability

Question 2

Mean

Answer 2

Sum of observations/ number of observations

Question 3

Median

Answer 3

The level below or above half of the observations fall

Question 4

Calculating median

Answer 4

Arrange in numerical order count how many values

If odd decide by 2 and round up to get position of median number

Even = decide by to go to the number in that position and average it with the number next highest

Question 5

Mode

Answer 5

Most frequent occurance

Question 6

calculating mode

Answer 6

Arrange in numerical order and number that appears most is the mode can have more than one

Question 7

Example: do mean median mode of 1,1,2,3,4,5,24

Answer 7

Question 8

Notation for population mean

Answer 8

“U” or mu

Question 9

Notation for population standard deviation

Answer 9

sigma= o
Sd

Question 10

Notation for population variance

Answer 10

Sigma squared
O^2

Question 11

Normal and positive and negative skewed distributions

Answer 11

Question 12

When to use median vs mean?

Answer 12

Median is better than mean for skewed date

Outliers can greatly skew the mean

Question 13

What direction is skew?

Answer 13

In the direction of the tail

Can be negative or positive

Question 14

What is probability

Answer 14

The numerical expression of the likelihood of occurrence

Question 15

Simple conditional probability

Answer 15

At the likelihood of one event occurring

Question 16

Conditional probability

Answer 16

Looks at two events occurring in relation to one another it looks at the probability of a second event occurring based on the probability of the first event occurring

Question 17

Complex probability

Answer 17

Used to calculate the probabilities of independent events

Question 18

Independent events

Answer 18

Those events whos occurance is not dependent on any other event

Question 19

Mutually exclusive events

Answer 19

Events that cannot occur at the same time

Question 20

Multiplication rule

Answer 20

Is used to calculate the probability of independent events both occurring

A and B

Pr = Pr (a) x Pr (b)

Question 21

Addition rule

Answer 21

Used to calculate the probability of independent events either occurring

A or B

Pr = Pr (a) + pr (b)

Question 22

Target population

Answer 22

The population to which it might be possible to extrapolate results from a study

Question 23

Study/source population

Answer 23

The population from which the study subjects are drawn

Question 24

Sampling frame

Answer 24

Are avalible and we are able to sample

Question 25

Sample

Answer 25

Consists of individuals that end up in the study

Question 26

Measurement error

Answer 26

Goal of designing a study is to accurately reflect your population of interest All measurement susceptible to error

Question 27

What are the two types of measurement errors

Answer 27

Random error (imprecision) Systemic error (bias)

Question 28

Sampling error

Answer 28

Is a bias in which a sample is collected in such a way that some member of the intended population have a lower or higher sample probability and others Bias

Question 29

How can you reduce systemic bias

Answer 29

Through random sampling giving everyone equal chance to be choosen

Question 30

What are the 4 types of random sampling

Answer 30

Simple random sample Systematic sample Stratified sample Cluster sample

Question 31

Random sampling

Answer 31

Attempts to replicate the characteristics of the target population using a sample Unbiased random sampling does not guarantee a replication of the target population characteristics

Question 32

Standard error of measurement

Answer 32

Random error Variability of a sample statistic Sources = natural imprecise individual differences

Question 33

Systematic error vs random error

Answer 33

Question 34

Confidence intervals

Answer 34

Surround point estimate with marginal error

Question 35

Confidence level

Answer 35

Is a measure of a degree of reliability of a confidence internal Higher confidence level more strongly we believe that the true value of the parameter being estimated lies within the interval