Chapter 5- Sampling and Probability Flashcards
What is random sampling?
Random sampling is one in which every member of the population has an equal chance of being selected into the study. Ideal and more likely to lead a representative sample. Expensive and difficult to achieve
What is convenience sampling?
Convenience sampling is one that uses participants who are readily available. Less expensive and easier than random sampling. Used most often.
What is generalizability?
Generalizability is the researchers ability to apply findings from one sample or in one context to other samples or contexts. Also called External Validity
Explain the external validity principle
If you don’t have sufficient gernalizability, you can never be certain that results from your sample apply to the larger population.
What is the goal of samples?
The goal of samples is to create a sample that represents our population of interest
What is independent sampling?
Independent sampling means each person selected had no influence over other people selected
If sampling is not random and independent, what can happen?
Resulting sample may be biased
What is the difference between random sampling and random assignment?
Random sampling is the method participants are assigned to a sample; Random assignment is the method which individuals within a sample are assigned to a condition.
What is a convenience sample?
Convenience sample consist of participants who are readily available. Convenience samples may not be generalizable to population. This method of sampling is used very often in social sciences.
What is a volunteer sample?
Volunteer sample is when participants self-select themselves to be in a sample. Like convenience, they may not be generalizable to population
What is replication?
Replication is doing the study again with different samples.
What is a sampling error?
A sampling error is the discrepancy of what the sample looks like versus what the population looks like.
What are inferential statistics?
Inferential statistics utilizes sample data to generalize to larger population. This is done by using probabilities.
What is probability?
Probability is the likelihood something will occur out of all possible outcomes
Why should we care about probabilities?
Probability theory helps us determine how likely are sample results are to occur given a hypothesis. Nothing is for certain and to make a conclusion
What is personal probability?
Personal probability is the likelihood something will occur based on one’s opinion. Subjective
What is expected relative-frequency probability?
Expected Relative frequency probability is the likelihood that an event will occur in the long run. A proportion of times the event occurs after many trials
What is a trial?
A trial is each time a procedure occurs
What is an outcome?
An outcome is the result of the trial
What is success?
Success is when the outcome you were interested in occurs
What is the law of large numbers?
The law of large numbers is as the numbers of the trials increase, our observed probability will approach the expected relative frequency probability
Describe probability vs. proportion vs. percentage
Probability is the long term proportion; Proportion is the success divided by the total trials; Percentage is the probability or proportion multiplied by 100
Individual trials must be independent. Explain this.
Independent means the outcome of each trial must not depend in any way on the outcome of previous trials. Each trial is independent from other trials
What are 2 types of errors that can occur?
Type 1 and Type 2
What is Type 1 error and Type 2 error?
The easiest way to think about Type 1 and Type 2 errors is in relation to medical tests. A type 1 error is where the person doesn’t have the disease, but the test says they do (false positive- REJECT THE NULL). A type 2 error is where the person has the disease but the test doesn’t pick it up (false negative- FAIL TO REJECT THE NULL).
What is the null hypothesis?
Null hypothesis- it proposes that nothing will happen–nothing is going on.
What is the alternate hypothesis?
The alternate hypothesis (research hypothesis) states there is a difference between populations, positive or negative. This is what the researcher anticipates
