Sampling, Measurement, Hypothesis Testing Flashcards
Those participating in a study constitute a ______
sample
The sample may be considered a subset of a general group called the ________
population
When the sample reflects the attributes of the target population it is ________
representative
When the sample does NOT reflect the attributes of the target population it is ______
biased
Random sampling
Each member of the population has an equal chance of being selected as a member of the sample
Stratified sampling
The proportions of important subgroups (ex; female and male) in the population are represented precisely
Cluster sampling
The researcher randomly selects a cluster of people all having some feature in common
Convenience sample
A group of individuals who meet the general requirements of the study are recruited in a variety of non-random ways
- Often form the “subject pool”
Sometimes a specific type of person is recruited for the study. This is a convenience sampling strategy called…
purposive sampling
Quota sampling
- Attempts to accomplish the same goal as stratified sampling (representing subgroups proportionally)
- Non-random
- May use “subject pool” to recruit participants
Snowball sampling
Researcher asks people who already completed their study to recruit additional subjects
Researchers develop measures from ______
constructs
Construct
Hypothetical factors that cannot be observed directly but is inferred from certain behaviours
Constructs are defined using…
operational definitions
Attention span as the _____ and letter identification as the…
construct, behaviour to measure the construct
Burnout as the ______ and score on self-reported Burnout index as the…
construct, behaviour to measure the construct
Determining is a measure is any good requires assessing two key factors:
- Reliability
2. Validity
Reliability
- Results are repeatable
- If there is a lot of measurement error, reliability is low and vice versa
Validity
Measures what it is designed to measure
Content validity
Whether the content of the items on a test make sense in terms of the construct being measured
Face validity
Whether the measure seems valid to those who are taking it
Criterion validity
Whether the measure is related to some behavioural outcome or criterion that has been established prior to research
Criterion validity: Predicative
Whether the measure can accurately forecast some future behaviour
Criterion validity: Concurrent
Whether the measure is meaningfully related to some other measure of behaviour
Construct validity
Whether a test adequately measures some construct and it connects directly with the operational definition
Accumulates as research produces supportive results
Construct validity: Convergent
Scores on a test measuring some construct should relate to scores on other tests that are theoretically related to the construct
Construct validity: Discriminative
Scores on a test measuring some construct should NOT be related to scores on other tests that are theoretically unrelated to the construct
Validity assumes reliability but…
reliability does not assume validity
Nominal scales
- The number we assign to events serves only to classify them into one group or another
- Studies using these scales typically assign people to names of categories and count the number of people falling into each category
Ordinal scales
Sets of rankings, showing the relative standing of objects or individuals
Interval scales
- Each unit increase in the scale is assumed to reflect the same change in the underlying measure
- Zero does not mean the absence of an attribute
- Think temperature
Ratio scales
- Each unit increase in the scale is assumed to reflect the same change in the underlying measure
- Zero does mean the absence of an attribute
- Think height
Descriptive statistics
Summarize data collected from sample
Inferential statistics
Allow you to draw conclusions about your data that can be applied to the wider population
Descriptive statistics include…
- Measures of central tendency
- Measures of variability
- Measures of association
Inferential statistics include…
hypothesis testing
When is the median useful?
When scores are very different from the rest it is beneficial to calculate the median. This is because the mean with give a distorted view
When is the interquartile range useful?
Useful for the same reason the median is useful - when there are outliers
The variance and standard deviation rely on the mean and thus…
should only be used when data is fairly normally distributed
On a Normal Distribution, 68% of all scores…
falls within a single standard deviation on either side of the mean
On a Normal Distribution, 95% of all scores…
fall within two standard deviations on either side of the mean
If you reject the null, you are rejecting the idea that…
there is no difference or relationship between conditions and saying that there is a statistically significant difference between conditions
If you fail to reject the null, you are failing to reject the idea that…
there is no difference or relationship between conditions and saying that there is no statistically significant difference between conditions
If p-value is LESS than alpha (0.05)…
Conclude that there is a statistically significant difference between conditions
Type I error
Rejecting the null when it is in fact true is called a Type I error
There is no real difference but you think there is because of the results in your study
Type II error
When you fail to reject the null but you are wrong
There really is a difference but you failed to find it in your study
Confidence intervals
Based on the data for a sample, we can be 95% confident the calculated interval captures the population mean
Non-overlapping confidence intervals indicate…
a meaningful difference between the two conditions of the study
Power
The chance of being able to reject the null when it is in fact false is referred to as the power of the statistical test
A test is said to have high power if it results in a _____ probability that a real difference will be found in a particular study
high
As power increases, the chance of a _____ error decreases and vice versa
Type II
