Biology simple sampling
Classified in Psychology and Sociology
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1. Problem statement: articulates the problem and an argument that explains the need for the study. 2.Purpose statement:aim of the study. 4.Independent variables: Presumed
Cause/influence,Will
Cause change in outcome of interest,May
Be an intervention Dependent Variable: presumed effect, outcome variable,variable researchers are trying to understant, explain, predict. 7.Experimental: RCT, QUASI,Nonexp(observational): decriptive, Cross-sectional,cohort, case control, 8. RCT a:Best
Evidence that the intervention caused the outcome,Gold
Standard;Causation;Multiple
RCTs can become Meta-analysis D:Many
Research variables cannot be manipulated (either realistically or ethically;May
Not be possible to randomize into group; Subject
To the Hawthorne Effect; Quasi A:Enhanced
Practicality;Some
Control;Participants
Are not always willing to be randomized D:Cause
And effect hampered (something else may have affected the change in the DV);Non
Equivalence between groups; NONEXP A:Studies
Problems that cannot be conducted experimentally;Can
Gather information on relationships between multiple variables;Experimental
Studies are often dependent on starting with descriptive correlational.D:No
Causation;Self-selection
– groups within a study that form themselves (male vs. Female; smokers vs. Non
Smokers) 9. Manipulation-is there an intervention Observation- when are the researchers collecting data, how often Randomization Control - how many groups are being compared.10.Counterfactual-What is done to the control group instead of the intervention in exp and quasi exp: no intervention, no treatment, Alternative treatment, Placebo,Standard care or usual care, Modified treatment (lower dose , partial intervention), delayed treatment(waitlisting control group). 12. Probability - (random)Each
Element of an accessible populationhas an equal independent chance of being
Selected to the sample.>Simple
Random Samplin Requires a sampling frame List of all available members in the
Population E.G. Telephone book All students at RRC>Stratified
Random Sampling The sampling frame is divided into 2 (or
More) list based on strata and random sampling is completed from each list
Separately Sampling via homogenous subsets
(proportional to population demographics) Proportionate sample Disproportionate sample – for comparison
Studies>Cluster
Sampling Successive random sampling –multistage
Sampling>Systematic
Sampling Every kth case – 10th, 5th, 3rd, 2nd The kth number is known as the “sampling interval”>NonProbability-(non random)>Rarely
Representative of the target population (i.E. Much larger sampling bias/error
Will result)>Elements
Do not have an equal chance of selection in the sample and often are referred
To as “self-selected>Non-representative
– readily available individuals are rarely typical of a population>Convenience uses most available (everyone in target
Population approached if target pop. Is small) Volunteers Newspaper ads or poster and pamphlet
Campaigns Snowball” -- network/chain sampling/word
Of mouth Useful as a starting way to obtain a
Sample when little is known about a topic>Consecutive
Sample: Recruitment of all people from
An accessible population over time -- in situations where names are
Continuously added to a list or new cases are diagnosed on a regular basis
(“rolling enrollment”) E.G.
Surgical waiting lists, new pregnancies added to a obstetrics team patient
List, new hip fractures, new bed sores. >Quota proportional representation of population
Strata(e.G. Gender; ethnicity) Works well in consecutive sample
Scenarios where you are likely to get an underrepresentation of a particular
Strata by convenience alone.>Purposive matching a comparison group in a
Quasi-experimental study Other purposeful choosing of experts on a
Topic.14.Predicts the appropriate sample size ex The power analysis predicted an ideal sample for this study, to
Make the statistics be as reliable as possible (and reduce the risk of poor
Statistical conclusion validity), would be 89 participants. 16.Informed Consent>letter signed by participants, implied consent(return of the questionnaire,Process consent(ongoing qualitative); Confidentiality Procedures>anonymity number rather than names, Securing information>Debreifing and Referals,sharing findings,venting sessions,reffering to health social psychological services.18. T-test
– used to test the statistical significance of a difference between means of
Two groups (t) Parametric (assumption of a normal curve) Independent group t-test (means of different groups) Dependent group t-test or paired t-test (means of same group
E.G. Before-after)One tailed or two tailed>ANOVA
– Analysis of Variance – measures significant differences in means of three or
More groups (F) Parametric (assumption of a normal curve) F-ratio Multiple comparison procedures (post hoc
Tests) – to find out which group caused the significant difference Repeated measures ANOVA – when means are
Compared at different points in time (pretest to posttest 1 and posttest 2)>Chi-squared
Test (χ2) Non-parametric test (does not require a
Normal curve) Compares the differences in proportions
In 2 or more groups, with variables with a small number of categories, Nominal data/ordinal, 2 x 2 crosstab table, Friedmans also an (χ2) used with larger category nominal/ordinal.>Correlation Coefficients, Pearsons(r),parametric, r=magnitude and direction of a relationship between two variables, Any correlation greater than r=0.70 is considered strong. >Multivariate SA deals with comparing three or more variables simultaneously.>Multiple regression uses F tables when squared R2.>Ancova combo of anova and multiple regression F statistics.>Manova Multivariate and anova