Question

1. Which of the following is NOT a way to reduce random error?

1. Increase sample size
2. Change study design
3. Randomization
4. Improve instrumentation
5. Ensure representativeness

2. True/False: Random errors are more serious for the validity of a study than systematic errors.
3. A group of women with a family history of breast cancer enroll themselves into a study that aims to reduce incidence of breast cancer. This is an example of what type of bias?

1. Surveillance bias
2. Nonresponse bias
3. Recall bias
4. Prevarication bias
5. Misclassification

4. Which of the following is NOT a criterion for confounders?

1. A risk factor for the disease
2. Associated with the exposure
3. An intermediate step in the causal path between exposure and disease
4. None of the above

5. Evaluating the effect of an exposure within levels of the confounder is what strategy to control for confounding?

1. Matching
2. Stratification
3. Restriction
4. Randomization

Answer 1

E. Ensure representatives does not reduce the random error

false.Random errors and systematic errors are important issues in the laboratory quality control process. Random errors are unavoidable and occur due to imprecision of an analytical method. On the other hand, systematic errors have certain characteristics and are often due to errors in measurement using a particular assay. Because random errors cannot be eliminated or controlled, the goal of quality control in a clinical laboratory is to avoid or minimize systematic errors. Usually recalibration of the assay is the first step taken by a clinical laboratory technologist to correct systematic error, but more serious problems such as instrument malfunction may also be responsible for systematic errors.

3.A survilliance bias:is correct ans.

Surveillance bias, also known as detection bias, arises when patients in one exposure group have a higher probability of having the study outcome detected, due to increased surveillance, screening or testing of the outcome itself, or an associated symptom.

Nonresponse bias is the bias that results when respondents differ in meaningful ways from nonrespondents. Nonresponse is often problem with mail surveys, where the response rate can be very low.

Prevarication bias occurs when a study subject over- or under-estimates outcome because of knowledge of the kind of treatment they had received.

recall bias when subjects have problem in recalling the information

4 C

1. The confounding factor must be associated with both the risk factor of interest and the outcome.
2. The confounding factor must be distributed unequally among the groups being compared.
3. A confounder cannot be an intermediary step in the causal pathway from the exposure of interest to the outcome of interest

5.C Restriction

• randomization -aim is random distribution of confounders between study groups
• restriction -restrict entry to study of individuals with confounding factors - risks bias in itself
• matching -of individuals or groups, aim for equal distribution of confounders
• stratification -confounders are distributed evenly within each stratum