STATS - describing variables/ shapes and distributions

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what is an independent variable?
the variables you manipulate
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what is a dependent variable?
the variable you measure
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what are predictor variables?
when you cannot manipulate the variables, but you use this as a form of IV to predict another variable or outcome
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what are outcome variables?
what you think may be affected by other factors, but you cannot necessarily measure, it is a form of the dv
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what are the four levels of measurement?
nominal, ordinal, interval and ratio
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what are nominal variables?
we use numbers to label them but they tell us what category pps are in i.e 1 = male, 2 = female
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what are ordinal variables?
we use a scale that implies an order, but doesn't tell us how much ranks differ i.e first and second place
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what do continuous measures consist of?
interval and ratio variables
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what are continuous measures?
there are equal distances between variables i.e the difference between 1 and 5 is the same as 7 and 11
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what are interval scales?
interval scales have no absolute zero point, e.g Celsius, as a temperature of zero doesn't mean that temperature doesn't exist at that point.
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what are ratio scales?
have an abolsute zero point, i.e weight, as if something has 0 weight this means the weight does not exist.
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what is between participants design/ comparative design? e.g?
compares the scores of one group of pps with another, i.e boys vs girls
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what is within participants design/ repeated measures
the researcher measures two or more variables at the same time using the same pps
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what are experiments?
where researchers manipulate the IV in order to determine cause and effect
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what is a correlational study/ survey method?
researchers gather info on different variables and observe how they are related, i.e measurement without manipulation.
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what are continuous variables?
variables which are given numerical values i.e age, income etc.
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what is raw data?
measures taken from each person in the sample
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what are descriptive statistics?
visual and numerical ways to present the key features of the raw data
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what are pie charts?
show the size of each group through percentages
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what are bar charts?
show the size of each group based on the height of the bars
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what do estimates of central tendency include? what is their overall purpose?
mean, median and mode - overall purpose is to identify the location of scores on a scale
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what do measures of dispersion include? what is their overall purpose?
range, variance and interquartile range - overall they quantify how much the scores vary
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what is the mean? what is it sensitive to?
the average of scores, very sensitive to outliers
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what is the median? what if the set is an even number?
the median is the middle score, if there is an even number of scores then the two central values are taken and divided by 2 to find the median
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is the median sensitive to outliers?
less affected by outliers than the mean
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what is the mode? are they sensitive to outliers?
the most occurring value, least sensitive to outliers
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what is the range? sensitive to?
difference between highest and lowest score, most sensitive to outliers
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what is the interquartile range? is it sensitive to outliers
remove the highest and lowest 25% of data, leaving the middle 50% from which you calculate the range. Much less sensitive to outliers
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what is the variance?
calculate the mean, subtract the mean from each data point, square each of these results and find the sum of these squared values, then divide this by the number of cases
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what is the point of variance?
to determine how much the data is spread about the mean
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what are the problems with variance?
it can't be interpreted on it's own (must calculate mean etc) and it is not in the original units (squared units instead).
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what is a normal distribution?
when the mean, median and mode are all the same and the data points cluster evenly about them, 50% values greater than mean and 50% values lower than mean.
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what is skewness?
how lopsided or asymmetrical the frequency curve is.
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what is a negative skew?
more scores on the left than the right, mean and median are smaller than mode
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what is a positive skew?
more scores on the right than left, mean and median higher than mode
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what is kurtosis?
the extent to which the frequency curve is excessively steep/ flat
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what is a leptokurtic curve?
a steep curve
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what is a mesokurtic curve?
a normal curve
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what is a platykurtic curve?
a flat curve
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what is a bimodal distribution?
when a distribution has two modes/ peaks
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what is a multimodal distribution?
many modes/peaks
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what is cumulative frequency distribution? example?
sum of the class and all classes below it, i.e get paid £250 for a week of work. The second week you get paid $300. Your cumulative amount for week 2 is £550.
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what is a percentile?
the percentage of cases that fall below a score in the distribution, i.e how many people did worse in a test.
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Other cards in this set

Card 2

Front

what is a dependent variable?

Back

the variable you measure

Card 3

Front

what are predictor variables?

Back

Preview of the front of card 3

Card 4

Front

what are outcome variables?

Back

Preview of the front of card 4

Card 5

Front

what are the four levels of measurement?

Back

Preview of the front of card 5
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