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67 Cards in this Set
- Front
- Back
descriptive stats |
summarizes a group of scores (mean, range, etc.) |
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inferential stats |
draw conclusions about something (t-test, correlations) |
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population |
all possible observations (US citizens, MSU students) |
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sample |
a set of observations from a population (300 MSU students) |
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parameter |
statistical info about a population |
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statistic |
information about a sample |
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2 variable types |
discrete and continuous |
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discrete |
-nominal and ordinal |
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continuous |
scale variables -interval and ratio |
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nominal |
qualitative - implies no rank/distance - EX. eye color, ID# |
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ordinal |
qualitative or quantitative - rank order but can not tell distance between - EX. getting 1st, 2nd, 3rd in a race w/o times |
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interval |
quantitative - rank order and distance between ranks |
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ratio |
quantitative - rank order, distance between ranks, and has a discrete zero point |
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independent variable (IV) |
variable we manipulate |
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dependent variable (DV) |
variable observed for chance bc of IV |
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confound |
any variable that could be cause the effect other than the IV |
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reliability |
consistency |
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valitidy |
measurement accuracy |
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hypothesis testing |
drawing conclusions about whether a relationship is supported by evidence |
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operational definition |
procedures used to measure/manipulate variables |
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within-groups |
all participants experience each level of the IV |
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between-groups |
each participant experiences only one level of the IV |
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describing distributions |
modality - kurtosis - skewness - description(describe the mean, mode, range) |
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unimodal |
1 peak - like normal curve |
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bimodal |
2 peaks |
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multimodal |
3+ peaks |
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positive skew |
tail is pulled to the positive side (right) |
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negative skew |
tail is pulled to the negative side (left) |
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kurtosis |
leptokurtic - platykurtic - mesokurtic |
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leptukurtic |
peaked "thin/pointy" distribution |
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platykurtic |
flat "plateau-like" distribution |
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mesokurtic |
normal curve - neither leptokurtic nor platykurtic |
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central tendency |
descriptive statistics that best represent the center of a data set |
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symmetrical normal distribution |
mean = median = mode |
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positively skewed distribution |
mean > median > mode |
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negatively skewed distribution |
mean < median < mode |
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variability |
how spread out the data is |
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deviation scores |
D - the amount a score differs from the mean |
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sum of squares |
SS - solves the summing deviation scores issue
SS= ∑(x-M)^2 |
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average |
s^2 - usual squared distance from the mean |
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variance of a sample |
s^2= ∑(x-M)^2 -------------- N-1
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variance of a population |
σ^2= ∑(x-M)^2 -------------- N |
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standard deviation of a sample |
s= √∑(x-M)^2 ---------------- N-1 |
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standard deviation of a population |
σ= √∑(x-M)^2 ---------------- N |
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random sampling |
a note on random |
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convenience sampling |
using readily available participants EX. most universities use this |
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volunteer sample |
a type of convenience sampling - aka "self-selected" sample - can be very biased |
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confirmation bias |
pay attention to information that confirms our initial beliefs |
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illusory correlation |
believing an association exists when it does not |
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personal probability |
our own belief of the likelihood an event will occur - not how we think of it in statistics |
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probability definition |
the actual likelihood an outcome will occur out of all outcomes success probability = ----------------- trials |
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percentage |
100x a proportion |
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proportion |
a proportion - always ranges from .00 to 1.00 |
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independent trials |
getting a result cannot effect the outcome of previous trials |
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hypothesis |
a statement that there is a difference between populations or sometimes, more specifically, that there is a difference in a certain direction - a guess as to what you think might be true |
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research question |
an observation, idea, or inquiry about a specific concern or issue |
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research hypothesis (H0 / H1) |
always think in terms of null - we only "reject" or "fail to reject" the null |
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the null hypotheses (H0) |
there is no relationship between the IV and DV |
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the alternative hypothesis (H1) |
there IS a relationship between the IV and DV |
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non-directional hypothesis |
H0 = acupuncture does not affect pain tolerance H1 =acupuncture affects pain tolerance |
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directional hypothesis |
H0 =acupuncture does not affect or decrease pain tolerance H1 =acupuncture increases pain tolerance |
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p value |
the probability that the numerical results we observed were due to chance alone EX. p= .045 ... there is a .045 probability/4.5% chance that these results are due to chance |
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a value |
alpha - simply a decision criteria - usually set to a=.05 |
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reject the null when... |
p < a |
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type 1 error |
we reject the null but the null was true - alpha reduces this |
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type 2 error |
we fail to reject the null, but the null was false - beta value can reduce this |
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hypothesis testing (reference picture) |
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