Biostats exam 2

What is a central tendency score

a calculated value or measure that represents, or is typical of the ENTIRE distribution of scores

what are 3 examples of central tendency

Mean, median, mode

What is the definition of mean

arithmetic average of all scores

Mean is appropriate for ______ or ______ data but not _____ or ____ scaled data. 

appropriate for ratio or interval

NOT nominal or ordinal

The _____ is the point in a distribution that divides the scores in two equal parts

median

Median is appropriate for ____, ____, or ____ data, but not ____. 

Median is appropriate for ratio, interval, or ordinal data, but not nominal. 

The ______ is the most frequently appearing score(s) in a distribution

mode

If there is 2 modes, known as ____ _____

bimodal distribution

Mode is appropriate for ____ and _____ data. 

ordinal, nominal

the ____ _____ is the best estimate of the population parameter μ. 

weighted mean

Weighted mean formula

weighted mean = sum (number x weighting factor)/sum of all weights

What is variability

a measure of dispersion

how disperse a group of scores are from each other or the degree to which individual scores in a data set differ from one another.

what type of statistic is variability

descriptive

what are 3 measures of variability

Range, Interquartile Range, Standard Deviation

Range calculation

HIGHEST score in a data set minus the LOWEST score. 

What is the interquartile range

A range of scores that make up the middle 50% of the distribution of scores (between the 25th percentile score and the 75th percentile score)

IQR calculation

75th percentile - 25th percentile

What is standard deviation

a calculated number that represents the average deviation (distance) between the mean and the observed scores

what are the 3 types of standard deviations

What is the difference btwn standard deviation of population vs sample

population: its Greek symbol is σ and it is a parameter.

• used when known, if unknown, use estimate

sample: Represented by capital S because it is a statistic. 

• Calculation: Find the deviation score, a raw score in a data set, minus the mean.

Raw scores greater than the mean have ______ deviations. 

Raw scores less than the mean have _____ deviations.

greater= positive

less= negative

what is the formula for standard deviation

What is the formula for the raw score method of standard deviation

Adjusted Standard Deviation (Ŝ) formula

What is the difference between Ŝ and σ

same formula but Ŝ is N-1

What is variance

another descriptive statistic that is also a measure of dispersion (variability); more helpful in inferential statistic calculations

σ²

S²

How to calculate variance from standard deviation

standard deviation squared

What is a z score

combines a raw score (X) with the mean and standard deviation of a distribution to know the relative standing of the raw score in that distribution

What is the purpose of a z score

extracts meaning from a distribution of scores, shows score’s relationship to the mean and standard deviation

aka standard score

Z score formula

what are the 3 distributions that are shown in a box plot

Central tendency (mean, median)

Variability (range, standard deviation)

Form or shape (normal vs skewed)

what does the dot in the box of a box plot mean

Mean (X̄)

what does the vertical line in the box plot mean

median

what do the left and right sides of the box mean

25th and 75th percentiles

what do the whiskers/horizontal lines mean

range

what kind of box plot distribution is this

normal distribution

what kind of box plot distribution is this

positive skew

what kind of box plot distribution is this

Negative skew

In a positive skew, how does the mean relate to the median

Mean > Median 

In a negative skew, how does the mean relate to the median

Mean < Median 

What does the effect size show

a calculation that allows us to answer the following question: “How much difference is there?” or “How meaningful is the difference?”

what is the formula for effect size

What does d < 0.2 mean

meaningless effect size

what does d=

what does d= 0.5-0.79 mean

medium effect size

what does d= 0.80 or larger mean

large effect size

what is univariate vs bivariate data mean

univariate= one variable data

bivariate= relationship btwn 2 variables