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44 Cards in this Set
- Front
- Back
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what is the difference between inferential and descriptive statistics?
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descriptive statistics communicate numerical information whereas inferential statistics use sample data to make estimates about the general population
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what are the 4 types of variables?
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nominal- observations that have categories
ordinal- variable for observations with rankings interval- has numbers as values where the distance between pairs of consecutive numbers is equal ratio- interval variables with a meaningful zero point |
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which variables are scale variables?
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interval and ratio
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what is the difference between discrete variables and continuous variables?
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discrete only represented by specific whole numbers and continuous variables are those with great decimal precision
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what is a confounding variable? how are they controlled?
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a variable that varies with the independent variable so cannot determine which variable affects the dependent variable.
they're controlled by randomly assigning participants to conditions as to spread the confounding variable across the the different conditions to neutralize effects |
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what is an operational definition
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the operations or procedures used to measure or manipulate independent or dependent variable
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what is the difference between experimental research and correlational research
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experimental research randomly assigns participants to conditions or levels of independent variable. it determines how an independent variable causes an effect on the dependent variable
correlational research is used when random assignment isn't possible. it examines how variables are related to each other |
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what's the difference between reliability and validity
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reliability- consistency of a measure
validity- extent to which a test measures what it was intended to measure |
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what's the difference between "between-groups" and "within-groups" designs?
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between: experience only one level of the independent variable
within: different levels of the independent variable are experienced by all participants in the study |
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the key difference of a histogram to a bar graph is
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- uses scale data
-values of variable on x-axis, frequency on y-axis |
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what is the difference between a histogram and a frequency polygon
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line graph with x-axis representing midpoints of intervals and y-axis representing frequency, dots are connected
histogram uses bar graph |
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positive skew has tail to ____, negative skew has tail to ____
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+ = right
- = left |
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the word distribution in statistics means
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the overall pattern of data
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False face validity lie
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falsely appearing to represent what it says but when you investigate further it doesn't.
e.g. labelling a variable "aggression" when really what's measured how many times a family shouts at each other |
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biased scale lie
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slants information in a particular way.
e.g. having the ratings for a college course using 3 positive words, one strong negative word and one ambiguous word. people will therefore give more positive ratings because most of the choices are positive |
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sneaky sample lie
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people chosen to participate in a study are selected so that the data will turn out in a particular way
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extrapolation lie
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assumes knowledge outside the study. (patterns will continue)
e.g. CB radios in 1976 declared that the popularity of CB radios would increase so much so that instruction would be taught in schools. |
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inaccurate values lie
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telling the truth in one part of data but visually distorting it in another place
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outright lie
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making up data to make weak arguments seem more legitimate
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scatter plot
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relationship between 2 scale values
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line graph
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relation between 2 scale values
- sometimes change over time (time plot) - sometimes predicted y score for x value |
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bar graph
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independent variable is nominal, dependent variable is scale. is average value of dependent variable for each category
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pareto
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ordered bar graph with highest scoring on left - lowest scoring on right
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pictoral graph
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visual depiction of data with independent variable with few categories and scale dependent variable. uses picture to represent value on dependent variable
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give examples of chartjunk
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moire vibrations- patterns to fill bars
grids- background pattern for graphs ducks- data dressed up to be something other than merely data |
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how can we tell whether two variables are linearly or nonlinearly related
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with a scatterplot. if forms a straight line, it's linear. if it forms a line that changes directions a nonlinear relation may be present. if data shows no relation its possible the 2 variables are not related
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what is the difference between a bar graph and a pareto chart?
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bar graph is visual depiction of nominal independent variable and dependent is scale. each bar represents mean value of dependent variable for each category
pareto is specific type of bar graph which categories on x-axis are ordered from highest bar on left to lowest bar on right |
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what are pictoral graphs and pie charts
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pictoral graph is visual depiction of data used for nominal independent variable with very few levels and scale dependent variable using picture or symbol to represent its value on scale dependent variable
pie chart is graph in shape of circle with slice for every category. the size of each slice represents the proportion fo each category |
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why is it important to identify the independent variable and the dependent variable before creating a visual display?
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independent variable goes on horizontal x-axis and dependent variabel goes on vertical y-axis
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3.39- shrinking doctor
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shrinking doctor: replace pictures with bars. space the three years out in relation to actual values (1964 ahd 1975 are farther apart than 1975 and 1990) include a more descriptive title
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3.39 workforce participation:
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eliminate all pictures, falling line now indicates an increase in percentage. 40% is at top and 80% at bottom. make y-axis go from highest to lowest starting from 0. eliminate 3D effect to make lines easier to compare. clear data point for each year with tick mark for each number on x-axis
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explain how the mean mathematically balances the distribution
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mean takes into account actual numeric value of each score. it is the center balance point in the data
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when is the mode used?
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1. when score dominates distribution
2. to describe bimodal or multimodal distributions 3. when nominal data are summarized |
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how is the mean affected by outliers but not the median?
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because numerical value of outlier used in computation of mean whereas the median is only based on the data in the middle of the distribution not at the extremes where the outliers are
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what is the difference between standard deviation and variance?
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standard deviation is a measure of variability in terms of the values of the measure used to assess the values
the variance is squared values which do not make sense to us, which is why we square root the variance and report the value as the standard deviation |
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why do we study samples rather than populations?
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rare to have access to entire population so use samples and inferential statistics to estimate what's happening to population
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what is generalizability?
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refers to ability of researchers to apply findings from one sample to other samples in other contexts
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explain how normal is used in every day and how statisticians use it
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everyday = objects or events that are common
statiticians = to refer to distribution that conform bell--shaped curve with peak in middle where most observations lie |
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how does random assignment make up for a lack of random selection?
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RA is a process in which every participant has an equal chance in being in any of the experimental conditions avoiding bias
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how do probabilities and proportions capture the likelihood of an outcome?
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probability is statement of likelihood of an outcome over the long run
proportion is calculation of how often something occurred out of the number of trials performed |
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how does size of sample of scores affect distribution of data
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distribution gets more normal as sample size increases
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what is a z score
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way to standardize data, expresses how far data point is from the mean of its distribution in terms of standard deviation
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what does mew indicate? what about subscript M?
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mew indicates mean for a population. subscript M indicates population composed of sample means- means of all possible samples of a given size from a particular population of individual scores
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what does a z-statistic, a z-score based on a distribution of means tell us about a sample mean?
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tells us how many standard errors a sample is from a population mean
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