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PSY 311
Ch. 5 Book Notes and Lecture
| Term | Definition |
|---|---|
| One of the most critical issues in planning research is | the selection of research participants |
| Population | large group of interest to a researcher. Results generalized to entire population |
| Sample | small set of individuals who participate in the study, intended to represent population |
| The Target Population | the entire set of individuals who have the characteristics required by the researcher |
| The Accessible Population | a portion of the target population consisting of individuals who are accessible to be recruited as participants in the study |
| Representative Sample | a sample with the same characteristics as the population |
| The major threat to selecting a representative sample is | bias |
| Biased Sample | a sample with different characteristics from those of the population |
| Selection Bias/ Sampling Bias | occurs when participants or subjects are selected in a manner that increases the probability of obtaining a biased sample |
| _____ is the simple observation that a large sample is probably more representative than a small sample | First Principle |
| Law of Large Numbers | larger the sample size, the more likely it is that values obtained from the sample are similar to the actual values for the population |
| Another factor influencing sample size is | research ethics |
| One helpful guide is to look at past | research studies to see how many participants they used |
| Sampling | the process of selecting individuals for a study |
| Sampling methods fall into 2 basic categories: | probability and nonprobability sampling |
| Probability Sampling | the odds of selecting a particular individual are known and can be calculated. |
| 3 important conditions of probability sampling | 1. the exact size must be known and must be possible to list all the individuals 2. each individual in the population must have a specified probability of selection 3. Selection must be a random process |
| Random Process | a procedure that produces one outcome from a set of possible outcomes |
| Nonprobability sampling | the population is not completely known, individual probabilities cannot be known, and selection is based on factors such as common sense or ease with an effort to maintain representativeness and avoid bias |
| Probability sampling is rarely used for research in the | behavioral sciences |
| What name is given to the group of individuals from which researchers actually select participants for research studies? | the accessible population |
| Simple random sampling | which each individual in the population has an equal and independent chance of selection, the starting point for most probability sampling techniques -each selection is independent of the others (does not influence or bias) |
| Process of simple random sampling consists of the following: | 1. Clearly define the population from which you want to select a sample 2. List all the members of the population 3. Use a random process to select individuals from the list |
| Often, a simple random sample is obtained by first assigning a | number to each individual and then use a random process to select numbers |
| 2 principal methods of random sampling are | 1. sampling with replacement 2. sampling without replacement |
| Sampling with replacement | individual selected for the sample to be recorded as a sample member and then returned to the population before the next selection is made |
| Sampling without replacement | removes each selected member from the population before the next selection is made |
| Systematic Sampling | a sample is obtained by selecting every nth participant from a list containing the total population after a random starting point -principle of independence is violated -as a probability sampling method, ensures a high degree of representativeness |
| Stratified Random Sampling | involves identifying specific subgroups to be included sample and then selecting equal-sized random samples from each pre-identified subgroup -useful when a researcher wants to describe each individual segment of the population or wants to compare |
| The main advantage of a stratified random sample is that it | guarantees that each of the different subgroup will be well represented with a relatively large group of individuals in the sample |
| Negative Consequences of Stratified random sampling | 1. tends to produce a distorted picture of the overall population 2. Not equivalent to simple random sampling |
| Proportionate Stratified Random Sampling | identifying specific subgroups to be included, determining what proportion of the population corresponds to each subgroup and randomly selecting individuals so that the proportion for each subgroup in the sample matches the corresponding proportion |
| Cluster Sampling | involves random selection of groups instead of individuals from a population |
| 2 advantages of cluster sampling | 1. quick and easy way to obtain a large sample 2. the measurement of individuals can often be done in groups, which can greatly facilitate the entire reserch project |
| Disadvantage of cluster sampling | it can raise concerns about the independence of the individual scores |
| Combined-strategy sampling | combine 2 or more sampling strategies to select participants |
| If each person in a large group has an equal chance of being included in an experiment, then what kind of sampling is being used? | random sampling |
| A teacher obtains a sample of children from a 5th grade classroom by randomly selecting the 3rd, 5th, and 8th rows and taking all the students in those rows. What kind of sampling is being used? | cluster sampling |
| A researcher would like to describe and compare the attitudes of 4 different ethnic groups of students at a local state college. What kind of sampling would be best to obtain participants for the study? | stratified random sampling |
| Nonprobability sampling methods: Convenience Sampling (Accidental/ Haphazard) | selection of individuals on the basis of their availability and willingness to respond; easy to get -weak form of sampling -used more often, less expensive, more timely technique |
| The most commonly used sampling method in behavioral science research is | convenience sampling |
| 2 strategies to help with most serious problem associated with convenience sampling | 1. ensure their samples are reasonably representative and not strongly biased 2. provide a clear description of how the sample was obtained and who the participants are |
| Quota Sampling | type of convenience sampling involving identifying subgroups to be included in the sample and then establishing quotas for individuals to be sampled from each group -sample probably biased |
| A researcher recruits a sample of 25 preschool children for a research study by posting an announcement in a local daycare center describing the study and offering a $10 payment for participation. What kind of sampling is the researcher using? | convenience sampling |
| A researcher would like to select a sample of 50 people so that 5 different age groups are represented. Assuming that the researcher does not know the entire list of people in the population, which sampling technique should be used? | quota sampling |
| Operationalize the variables | translate definition from abstract to concrete forms of observation or manipulation |
| Operationalization decisions | -Research tradition: has it been done before? -Theory: may suggest a certain operationalization -New measurement techniques: availability of equipment-may limit decisions |
| Self-report measures | people report on the variable -limited by self-awareness and honesty |
| Behavioral measures | observations -could be naturally occurring -or lab induced |
| Physiological measures | assessment of bodily states -Ex: brain imaging, heart rate, hormones -misattribution of arousal -accurate and objective -expensive -may not always reflect psychological processes |
| Misattribution of arousal | if you have intense steadily bodily of arousal, you take a look more to your surroundings to explain your bodily state |
| Quantitative | variables are assigned a numeric value -closed-ended questions, structured observations -data is easily analyzed |
| Qualitative | verbal description -open-ended questionnaires, unstructured observations -non-numerical data and expressed with language |
| True score | the actual score |
| Obtained score | the score the measure gives |
| Measurement error | the difference between true and obtained scores -want to minimize measurement error |
| Reliability: Does it give consistent measurements? | if the true score doesn't change, the obtained score shouldn't change -Physio measures tend to be more reliable than self-report and observation |
| Test re-test reliability | same test is given twice with a delay -not useful for unstable variables (mood) |
| Parallel-form reliability | different forms of the same test -Ex: GRE questions |
| Split-half reliability | top-half of questionnaire is compared to the bottom-half |
| Reliability of Observation: interrater reliability | 2 plus people record what they observe |
| Reliability of physiological measures | -test-retest reliability and interrater reliability |
| Self-report measures: 3 of them | test re-test, parallel-form, and split-half reliability |
| Construct validity | does this measure what I think it measures? |
| Face Validity | does it look like it measures what it should? |
| Content Validity | does it sample behavior it is intended to measure? |
| Predictive Validity | does it predict expected outcomes? |
| Convergent Validity | does it correlate with similar variables? |
| Discriminant Validity | does it not correlate with theoretically different variables? |
| Validity can change over time: Instrumentation threat | changes in the interpretation can affect results Ex: outdated items, questionnaire wording- ' I feel gay" |
| Adequacy of Measures: 2 problems | 1. Sensitivity: can it detect subtle changes or differences? 2. Range effects: maximum or minimum score is too frequently reached |
| Reactivity= | when observing someone changes their behavior -threatens the validity of all types of measures |
| Subject-expectancy effects | when participants anticipate the hypotheses and respond differently -intentionally or unintentionally |
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