Module 2: Study Designs and Sampling

Question 1

All sampling units are selectable

Answer 1

-every sampling unit in the statistical population must have some non-zero probability of being included in your sample (if there is both brown and black penguins and you state that the statistical population is all the penguins in the colony, then every penguin in the colony must have a chance of being included)

Question 2

Selection is unbiased

Answer 2

-avoid bias so that sample is a representation of larger statistical population, avoid using senses to select sampling units (don’t select only baby penguins because they are easier to catch)

Question 3

Selection is independent

Answer 3

-selection of one sampling unit cannot influence the probability that any other particular sampling unit is selected (can not interview anyone in same group)

Question 4

All samples are possible

Answer 4

-all samples that could be created from the statistical population are possible (if u are surveying both east and west sides of the city, composition must include sampling units from both the east and west sides)

Question 5

Observational studies

Answer 5

-based on observations from a statistical population, different from an experimental study because researcher has no control over the variables

Question 6

Goals and limitations of observational studies

Answer 6

-goals: characterize something about an existing population
-drawback: can provide associations but cannot provide causation conclusions

Question 7

Confounding variables

Answer 7

-uses explanatory variables (smoking) and response variable (lung cancer), but also includes confounding variables (age etc)

Question 8

Simple random survey (observational study design)

Answer 8

-identifies every sampling unit in the statistical population and then selecting a random subset of those to be in the sample (create list and randomly draw from it)

Question 9

Stratified survey (observational study design)

Answer 9

-when there are subgroups in statistical population that can influence the study results (if we wanted to estimate wages of people across canada, the data would be dominated by people in ontario, so we break population into strata with different weighting)

Question 10

Cluster survery (observational study design)

Answer 10

-create groups where the non-relevent heterogenity is contained within each group (children earn less than adults so if you are measuring household earnings you should sample each house, not each person)

Question 11

Case-control survey (observational study design)

Answer 11

-used to compare data between 2 groups, there is both a case and control group and the control group contains sampling units without the response variable of the case group

Question 12

Cohort survey (observational study design)

Answer 12

-follow sampling units over time, looking for the development of a particular response variable (outcome is unknown when the sampling units are selected)

Question 13

Retrospective vs prospective

Answer 13

-retrospective: studies where the outcome is already known
-prospective: studies where the outcome is not yet known

Question 14

Cross-sectional vs longitudinal

Answer 14

-cross-sectional: studies that the response variable are only taken at a single snapshot in time
-longitudinal: studies that the response variable is recorded at multiple points in time

Question 15

Experimental study

Answer 15

-goal is to study the effect of one or more manipulated variables on one or more response variables, by manipulating variables (are used to establish cause and effect among variables)

Question 16

Replication

Answer 16

-idea that a treatment will be repeated a number of times to see how repeatable a measured outcome is

Question 17

Pseudoreplication

Answer 17

-error in the design of an experimental study where the observation units are analysed rather than the sampling units

Question 18

Control treatment (experimental study)

Answer 18

-reference treatment to compare against the treatment levels that alter the explanatory variable

Question 19

Blocking (experimental study)

Answer 19

-analogous to stratified sampling but for experimental studies, it is used to control for variation among sampling units

Question 20

Blinded (experimental study)

Answer 20

-sampling unit alone (single blind), and sometimes also the researcher (double blind) does not know what treatment they are assigned to

Question 21

Placebo (experimental study)

Answer 21

-used for control treatment to help accomplish a blinded design, is a substance or treatment that has no affect on the response variable

Question 22

Sham treatment (experimental study)

Answer 22

-like gold standard drug/treatment