Basic science research
The kind of research conducted in a laboratory, and not on people
Control (standard)
An experiment or observation designed to minimize the effects of variables other than the independent variable
The use of controls also allows investigators to check for _____.
contamination of reagents
Positive controls
Positive controls are those that ensure a change in the dependent variable when it is expected.
Positive controls are often used to assess _____.
test validity
Negative controls,
Negative controls ensure no change in the dependent variable when no change is expected.
What is the purpose of a negative control?
The essential purpose of a negative control is to reproduce a condition that cannot involve the hypothesized causal mechanism, but is very likely to involve the same sources of bias that may have been present in the original association.
i.e. examines for confounding variables
Placebo effect
A beneficial effect produced by a placebo drug or treatment, which cannot be attributed to the properties of the placebo itself, and must therefore be due to the patient's belief in that treatment
A placebo is an example of a _____.
negative control
What are the two main advantages of being able to manipulate all of the relevant experimental conditions in a basic scientific experiment?
1. The effects of confounding variables can be minimized by using control groups.
2. Causality can often be established.
Causality is an _____ relationship.
if–then
Independent variable
the variable being manipulated
the "if"
Dependent variable
the variable being measured or observed
the "then"
What two conditions are necessary to establish causality?
1. The change in the independent variable always precedes the change in the dependent variable
2. The change in the dependent variable does not occur in the absence of the experimental intervention
The independent variable belongs on the _____ axis, and the dependent variable belongs on the _____ axis.
x-axis
y-axis
Replication
The repetition of the set of all the treatment combinations to be compared in an experiment
Each of the repetitions is called a replicate.
Accuracy
Accuracy, also called validity, is the ability of an instrument to measure a true value.
Precision
Precision, also called reliability, is the ability of the instrument to read consistently, or within a narrow range.
A 170-pound person standing on a scale that is _____ may get readings between 150 and 190 pounds.
accurate but imprecise
A 170-pound person standing on a scale that is _____ may get readings between 129 and 131 pounds.
inaccurate but precise
Bias is a _____.
systematic error
Systematic error
Systematic error always occurs, with the same value, when we use the instrument in the same way and in the same case.
Random error
Random error may vary from observation to another.
Random error is overcome by having a _____.
large sample size
Systematic error is overcome by using _____.
standardized procedures (same instruments, same conditions, same calibrations, same procedure, etc)
Precision is to _____ as accuracy is to _____.
reliability
validity