Research Methods/Scientific Method
Key Terms in Stats
Central Tendency
Graphs
Frequency Distribution
100
Case Study
The case study is a descriptive technique in which one person is studied in depth. Sometimes studying the extraordinary helps us understand the ordinary. The case study is often used when studying individuals who are interesting to researchers because they are rare. Therefore, the individuals who serve as the focus of case studies are not like most other people. Since the cases are so specific, the potential to apply what’s learned to the average person may be very limited.
100
Construct
Psychologists study ideas or concepts like happiness, memory, intelligence or anxiety. We want to Constructs are internal attributes or characteristics that cannot be directly observed but are useful for describing and explaining behavior.
100
Mean
The mean, also known as the arithmetic average, is computed by adding all the scores in the distribution and dividing by the number of scores. The mean for a population is identified by the Greek letter mu, (pronounced “mew”), and the mean for a sample is identified by
or
(read “x-bar”).
100
Histograms
Histograms provide a way of visualizing large sets of numbers
100
Random distributions
In random distributions, there is an equal probability of any option being chosen. Think of a coin toss.
200
Naturalistic Observation
Naturalistic observation is a descriptive technique of observing and recording behavior in naturally occurring situations without trying to change or control the situation. Jane Goodall's study of chimpanzees in the wild comes to mind when we think of this type of research.
200
Variable
A characteristic or condition that changes or has different values for different individuals is a variable. Variables can be numbers but they can also be classifications or descriptors.
200
Median
The median of a set of observations is the middle value. To find the median, first rank order the scores.
200
Bar graphs
Bar graphs typically display averages or frequencies by categories.
200
Normal distributions
Distributions of numbers can have a number of different shapes. Most of the time there are a few numbers larger or smaller than average.
Most measurable things in the world share some basic properties. If I measure enough of anything, most of the scores will pile up around the middle (average) but there will also be odd scores that are much higher or much lower than the average
300
Surveys
Surveys are a descriptive technique for obtaining the self-reported attitudes or behaviors of a group, usually by questioning a representative, random sample of that group.
300
Operational Definition
In order to study constructs, psychologists need to describe ideas using a number or measurement procedure (a set of operations) for measuring an external behavior and uses the resulting measurements as a definition and a measurement of a hypothetical construct. Note that an operational definition has two components:
- First, it describes a set of operations for measuring a construct.
- Second, it defines the construct in terms of the resulting measurements.
300
Mode
The mode is the score with the largest number of occurrences.
300
Line graphs
Line graphs are similar to bar graphs in that they display averages. The best use of line graphs is when one variable is ordinal or continuous.
300
Skew left/right
Left skew: A distribution that has a tail on the left has a left skew. In this case the mean and median are less than the mode because they are more heavily influenced by the scores in the tail (Mode > Median > Mean).
Right skew: A distribution that has a tail on the right has a right skew. In this case the mean and median are more than the mode because they are more heavily influenced by the scores in the tail. (Mode < Median < Mean).
400
Correlation Studies
A correlational study typically uses only one group of participants but measures two different variables (two scores) for each individual.
Correlations are used to make predictions. For example, it is possible to predict how tall people are if we know their shoe size because shoe size and height are correlated. We cannot predict IQ based on shoe size because shoe size and IQ are not correlated.
Importantly, a correlational study is used to examine the relationship between two variables but cannot determine whether it is a cause-and-effect relationship.
400
Parameter
A value that describes a population is a parameter. A parameter is usually derived from measurements of ALL the individuals in the population.
400
Nominal/Ordinal
Nominal: Since there is no particular order for nominal variables, the mode is the best option.
Ordinal: The median only makes use of the order information in your data (i.e., which numbers are bigger) but doesn't depend on the precise numbers involved. That's exactly the situation that applies when your data are ordinal scale.
400
Scatterplots
Scatterplots display two different variables or measurements from a group of individuals
400
For a perfectly symmetrical distribution, which relationship is always true?
mean = median
500
Experiments
Experiments involve manipulating one or more variables and measuring a different variable, Much of this course will cover different types of experiments and their associated statistics.
500
Descriptive vs Inferential Statistics
Descriptive statistics are statistical procedures used to summarize, organize, and simplify data.
Inferential statistics consist of techniques that allow us to study samples and then make generalizations about the populations from which they were selected.
500
Interval and Ratio (Continuous)
Either the mean or median is appropriate for continuous variables. The mean has the advantage
that it uses all the information in the data (which is useful when you don't have a lot of data). But it's very sensitive to extreme, outlying values. If your data has a few extreme scores, then the median more closely reflects the data as a set.
500
Pie chart
Pie charts are used to show the relative proportions different groups or categories. Typically pie charts are to show frequencies for nominal variables.
500
For a perfectly symmetrical distribution, which relationship is always true?
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