Errors

Question 1

Random errors

Answer 1

• fluctuations in either direction in the measured data due to the precision limitations of the measurement device
• often due to the researcher’s inability to take a measurement in the same way and get exactly the same result

Question 2

Systematic errors

Answer 2

• also called bias
• these are reproducible errors that are consistently in the same direction
• a problem which persists throughout the entire experiment is called bias

Question 3

Type 1 error

Answer 3

• incorrect rejection of the null hypothesis (false positive claim in favour of the research hypothesis
• likelihood of type 1 error is called alpha
• as long as it is less than 0.05 its ok and is less than the level of statistical significance

Question 4

What can lead to type 1 error?

Answer 4

-repeated testing of hypothesis using the same data, multiple subset analysis and secondary analysis as at least one test will be positive out of 20 if p is 0.05

Question 5

Type 2 error

Answer 5

• the incorrect acceptance of the null hypothesis, concluding no differences exist between two treatments actually exist (flase negative rejection of research hypothesis)
• probability of this is called beta
• usually due to small sample size or large variance
• 1-beta is the power of a study and is the ability to obtain a true positive

Question 6

Power

Answer 6

• ability to obtain a true-positive result

- power= 1- B

Question 7

Probability of type 1 error

Answer 7

-alpha or p value

Question 8

Probability of type 2 error

Answer 8

-beta

Question 9

Alpha

Answer 9

5%

Question 10

Beta

Answer 10

20%

Question 11

Power

Answer 11

80%