Frequency, central tendancy, variability, z-scores Flashcards
Parameters
Population values e.g. the mean income for the population was 46,000 per annum - 46,000 is a parameter
Sample
The individuals selected from the population and that you have gathered information on in your study or intend to do so.
Statistics
Sample values (the mean income for the sample was 44,88 per annum - 44,800 is a statistic
Sampling error
The discrepancy between the population parameter and sample statistic
Data
Many scores
Datum
One score
Data set
A collection of scores, usually on many different variables.
Experimental manipulation
-Drug, treatment
Control manipulation
- Active placebo (e.g. side effects same as drug)
- Passive placebo (e.g.) sugar pill
Independent variable (V)
- the presumed cause of some effect
- Experimentally manipulation
- Classifications or naturally occurring
Dependent variable (DV)
- Presumed effect of the IV
- The variable that is observed as a result of the manipulation or classification of the IV
Participant variables
Age, gender, ect.
Environmental variables
Temperature, time of day ect.
Discrete
When the measurements can only take on integer values (whole numbers, not fractions)
Continuous
When the measurements could conceivably take on any value in a continuum. (i.e. an infinite number of fractional parts)
Confounding variable
factors other than the independent variable that may cause a result.
Exaggerated variables
Use extreme differences between levels/groups of the IV (compare performance (DV) between no help (IV level one) vs. expert help (IV level 2)
Frequency distribution table
Shows the number of individuals with a certain value (or within a value range) on the measurement in question)
Measures of central tenancy
mode
median
mean
Distributions
Normal, negative/positive skew
Descriptive statistics
- Measures of central tendancy (mode, mean, median
- Distributions; Normal, Negative/positive skew
- measuring variability
- standard deviation
Measures of central tendancy
typical or average score in distribution
Mean
Arithmetic average of scores
Median
score falling in the exact center
Mode
most frequently occurring score
n
total number of scores in sample
Sigma (weird E symbol)
the sum of X, (add up all scores)
how do you find the median with an odd number of scores?
Order the scores from largest to smallest then it is the middle value.
how do you find the median with an even number of scores.
order scores from smallest to largest
then add the two middle scores together and divide by two.
Variability
How much scores vary from each other and from the mean
Standard deviation
Numerical depection of variability
- high variability in data set = high standard deviation
- Low variability in data set = low standard deviation
Normal distribution
Normal distribution is a symmetric, bell-shaped curve that represents the pattern in which many human characteristics are dispersed in the population.
Fixed pattern
how scores under the normal distribution are dispersed
What does standard deviation serve as
a unit of measurement
- about 68% of scores fall within one SD (plus or minus from the mean.
z-scores (standardized scores)
Used to describe the location of individual raw scores (X) on the distribution in standard deviation units
