Qualitative vs. Quantitative
Type of Sampling
Experiment vs. Observational Study
Type of Study
Bias
100

Eye Color

Quantitative

100

Each member of the population is equally likely to make up the sample.

Simple Random Sample

100

Investigator assigns treatments to the participants at random.

Randomized Experiment

100

Consist of Prospective, Retrospective, and Cross-Sectional studies.

Cohort Studies

100

Responses are skewed due to a strong opinion and a voluntary participation.

Voluntary Response Bias

200

Classify individuals into categories

Qualitative

200

A sample that is not drawn by a well-defined random method.

Sample of Convenience

200

Assignment to treatment groups is not made by the investigator

Observational Study

200

The general category branching into both cohort and case-control studies.

Observational Study

200

Outcome of leaving questions blank in a survey.

Non-response Bias

300

How much or how many of a condition there is.

Quantitative

300

The population is divided into groups, then a simple random sample is drawn from each group.

Stratified Random Sampling
300

Investigator wants to determine whether a certain drug will decrease depressive moods. They choose half of the sample to get the drug at random, and half to take a placebo. Mood is measured after 1 month.

Randomized Experiment

300

A study where measurements are taken at one point in time.

Cross-Sectional Cohort Study

300

When questions are worded in a way that encourages a particular response.

Leading Question Bias

400

Behavior

Qualitative

400

Items are drawn from the population in groups

Cluster Sampling

400

Differences in outcomes are due to chance or, in bigger differences, treatments.

Randomized Experiment

400

A group of subjects are studied OVER TIME to determine whether various factors of interest are associated with an outcome

Prospective Cohort Study

400

Often leads to the selection of analyses that correspond with the hypothesis... Happens when a researchers opinions are skewed.

Self-interest Bias

500

MRI data

Quantitative

500

Items are ordered. Every Kth item is chosen to be included in the sample

Systematic Sampling

500

An investigator wants to determine whether exercise decreases depressive symptoms. They send out a survey to the NIH asking participants to report their level of activity and level of depressive symptoms. Correlations are assessed.

Observational Study

500

A study in which two samples are drawn, one of which consisting of the people with the disease/case of interest, and the other of which consisting of the controls (no disease).

Case-Control Study

500

Some members of the population are more likely to be included in the sample than others.

Sampling Bias
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