Research Basics pt. 2 Flashcards
Parameter
-descriptive value for a population
Statistic
-descriptive value for a sample
Mean
-average
-most commonly used
-only used with interval/ratio
-influence by outliers
-toward the tail oppositte of mode
-Mu u
Variance
-SD^2 or (distance from mean)^2/ n-1
-Sigma^2
Standard Deviation
-distance between score and mean
- Square root (distance from mean)^2/ n-1
-Sigma
Frequency Distribution
-organized picture of an entire set of scores
-histogram, smooth curve, stem and leaf
Smooth Curve
-shows tthat the exact frequency is not being shown
-want it to be symmetrical (normal curve, mean and median are equal)
Histogram
-shows all the frequencies of the distribution
Skew
-non symmetrical distribution
-named for tail
Positive: scores pile up at low values, tail point to high values
Negative: scores pile ip at high values with tail at low
Kurtosis
-peakedness of tthe distrubution
Leptokurtic
-skyscraper
-higher and thinner peak
-low variability
-easier to get significance
Platykurtic
-hill
-lower peak
-higher variability
-harder to get significance
Stem-And-Leaf Display
-each score devided into a stem (first digit) or leaf (last digit)
Mode
-most frequent
-used in all data
-located on one side near peak, other farthest from mean
Median
-middle
-used for ordinal, intterval, or ratio
-unnaffected by outliers
-can’t show sig dif
-between mean and mode
Variabiltiy
-how spread out the data is
-descriptive (how spread out) and inferential stats (how accurate to pop)
-meaured by range or SD
More variability: less significance (platykurdic)
Range
-total distance
SD in Normal Distribution
-70% of scores 1 SD of mean (35+/-)
-95% of scores 2 SD of mean
-99% of scores 3 SD of mean
standardized, mean is 0
Z Score
-where a score is located relative to other scores
-# of SD above or below mean
-descriptive (where in curve) and inferential stats (reference to population)
z= score-mean/SD
Inferential Statistics
-infer things about the population based on sample