Experimentation P.2 Flashcards
Advantage and disadvantage of observational studies
Observational studies are good at detecting correlation, but since they do not directly test a hypothesis, they are less useful for determining causation.
Why is the purpose randomised block designs?
confounding variables must be held constant if possible, or at least monitored so that their effect on the results can be accounted for in the analysis. In cases where confounding variables cannot easily be controlled, a randomised block design could be used.
What’s the use of negative control?
The negative control provides results in the absence of a treatment.
what is positive control?
A positive control is a treatment that is included to check that the system can detect a positive result when it occurs.
What is the placebo effect?
Placebo effect is a measurable change in the dependent variable as a result of a patient’s expectations, rather than changes in the independent variable.
What are some ex. of in vitro?
Examples of in vitro experiment include: cells growing in culture medium, proteins in solution, purified organelles.
What factor determines the representative sample size?
The extent of the natural variation within a population determines the appropriate sample size; more variable populations require a larger sample size.
What should a representative sample size require?
A representative sample should share the same mean and the same degree of variation about the mean as the population as a whole.
What is ranked data?
Ranked data refers to the data transformation in which numerical values are replaced by their rank when the data are sorted from lowest to highest.
Difference b/n qualitative and quantitative data?
Qualitative data is subjective and descriptive. Quantitative data can be measured objectively, usually with a numerical value.
When does correlation exist?
Correlation exists if there is a relationship between two variables; correlation is an association and does not imply causation.
When does causation exist?
Causation exists if the changes in the values of the independent variable are known to cause changes to the value of the dependent variable.
When does a positive correlation exist?
A positive correlation exists when an increase in one variable is accompanied by an increase in the other variable.
When does a negative correlation exist?
A negative correlation exists when an increase in one variable is accompanied by a decrease in the other variable.
What determines strength of correlation?
it’s is proportional to spread of values from line of best fit i.e. how closely the points lie to the line of best fit.
