stats Flashcards
What is the mean?
the average
What is the median?
the middle number in a data set, half the data above it and half the data is below it
What is the mode?
the most occurring number in a dataset (no mode is possible, bimodal as well…)
What is the empirical rule in normally distributed data?
(in normally distributed data) most of the data points within the data set fall within three standard deviations of the mean
What percentage correlates with the empirical rule?
+- 1 standard deviation of mean = 68% of the data
…
2 = 95%
3 = 99%
What is an outlier?
A data point with an abnormal distance from the other values in the data set
What is probability?
Desired outcome / possible outcomes
What are permutations?
Describe the standard deviation.
The spread/scatter of the data around the mean in a bell curve of normal distribution (65-95-99 rule = 1,2 and 3 std devs have ex. 65% of the data at 1 standard deviation from the mean).
What is the standard deviation?
The “average” of the divergence from the mean of individual data points in a data set. The “average” is actually the root of the sum of the of the squared deviations. (individual deviation to the mean -> squared -> all individual squared deviations added all up -> divide by number of data points (n for whole population or n-1 for sample of it) -> take the square of that
What is variability?
how spread out the data is, range and standard deviation
What is the range of a dataset set?
It is the highest number minus the lowest
What is the z score?
A way to measure how far from the mean each of your data values is using a standardized scale.
What is the difference between discrete random variables and random variables?
discrete random variables: limited outcomes (number of drinks ordered, no decimals…)
random variables: limitless possible outcomes
each require different probability techniques!
How to find a weighted mean with discrete random variables?
Multiply discrete variable with relative frequency (ex. 3 drinks ordered by 4 people out of 40…3x0.1 = weighted mean of 0.3).
Adding weights is the weighted mean of a set of discrete random variable
What is variance? (mathmatically)
sum of squared difference between values and weighted mean squared and multiplied by relative frequency (not weighted) = variance.
What percentage of data points should be within 3 standard deviations (for normal distribution)?
99.7%
What is a binomial random variable?
…when an experiment only has two possible outcomes (positive or negative for a disease…vote or not vote…ex.)
In binomial experiments, when the probability is at 0.5 and number of events is very very large, there is what?
Normal distribution
In binomial experiments, when the probability is NOT equal to 0.5 and number of events is very very large, there is what?
asymmetry of non-equal probability is overwhelmed and the resulting distribution can be estimated with normal curve
