PSYC 1010 Study Guide - Midterm Guide: Square Root, Systematic Sampling, Normal Distribution

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Published on 18 Apr 2013
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Psych 1010 midterm 1 study notes
Chapter 1
- Branches of statistics
o Descriptive
Organize summarize and communicate numerical information
o Inferential statistics
Using data collected from a sample to draw conclusions about
a population
- Population: set of all observations in a particular study
- Sample: A set of observations drawn from a population of interest for
inclusion in a study
- Parameter: value that described population
- Statistic: value that describes sample
- Variables
o Discrete variables
Can only take on specific values (integers)
Measures how many
o Continuous variables
Full range of values
Measures how much
o Always discrete:
Nominal variables
Observations with names or categories as values
Qualitative not quantitative differences between
categories
Ordinal variables
Ranked by size or magnitude
Know rank but no info about size intervals
o Scale variables
Sometimes discrete, sometimes continuous
Interval
Observations of ordered numerical values with
intervals of equal size, no meaningful zero
Ratio
Observations of ordered numerical values with
intervals of equal size, but there is a meaningful zero
Can form ratios
- Operational definition
o Set of procedures used to measure or manipulate a variable
- Confounding variable
o Uncontrolled variable that it unintentionally allowed to vary
systematically with the independent variable
- Reliability
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o Consistency of measure
- Validity
o Extent that the test measures what it is supposed to measure
- Research designs
o Correlational method
Association between two or more variables
No manipulation, only observation
o Experimental method
Randomly assign participants to levels (groups) of the
independent variable
Able to make causal conclusions (effect of IV on DV)
- Control confounding variables
o Random assignment to groups
Chapter 2
- Frequency distributions: gives number of times each possible value of a
variable occurs in a data set
o Frequency table
o Grouped frequency table
Used for large range of scores and data to several decimal
places
Full range = Xmax Xmin +1
Use 10 intervals
No gaps
o Frequency histograms
Represent scale data (interval and ratio)
Can have polygon overlay (lines over bars)
o Frequency polygon
Also represent scale data (looks more like line graph)
o Grouped histogram
Use middle of interval at bottom (e.g 7.5 not 0-14.99)
o Grouped polygon
Same as histogram, use middle point
- Histograms vs. bar graphs
o Histograms are used for interval or ratio scales of measurement, bars
touch
o Bar graph bars do not touch, used for nominal or ordinal data
- Normal distribution
o Bell-shaped
o Symmetrical around the mean
o Unimodal (only one peak)
- Skewed distributions
o Positive skew
tail more to the right
May reflect floor effect (you can’t score any lower)
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Document Summary

Organize summarize and communicate numerical information: inferential statistics. Using data collected from a sample to draw conclusions about a population. Population: set of all observations in a particular study. Sample: a set of observations drawn from a population of interest for inclusion in a study. Can only take on specific values (integers) Observations with names or categories as values. Know rank but no info about size intervals: scale variables. Observations of ordered numerical values with intervals of equal size, no meaningful zero. Observations of ordered numerical values with intervals of equal size, but there is a meaningful zero. Can form ratios: set of procedures used to measure or manipulate a variable. Confounding variable: uncontrolled variable that it unintentionally allowed to vary systematically with the independent variable. Validity: extent that the test measures what it is supposed to measure. No manipulation, only observation: experimental method. Randomly assign participants to levels (groups) of the independent variable.

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