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41 Cards in this Set
- Front
- Back
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What are the three basic types of descriptive statistics?
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Measures of central tendency, measures of variation, measures of relative standing.
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Calculate the mean...
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The mean is the sum of the samples divided by the number of samples.
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Describe how the median is found...
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The median is the middle number in an odd set of samples. Its the average of the two middle numbers in an even sample.
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Describe the mode in a sample of numbers...
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The mode is the most frequently occurring number. If there is more than one mode, we refer to it is a bimodal or multimodal.
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What does bimodal mean?
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It means there are two sets of data that have the same number of occurrences.
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What is the range of a sample?
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Subtract the low and high values of the sample set
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Describe calculating the sample variation of a set of numbers...
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variation is the sum of the squares of the distance from the mean divided by (n-1).
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How is the z-score calculated?
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The z-score is the distance that the number is from the standard deviation.
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Describe two methods for detecting outliers...
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Z-score and boxplot
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What constitutes an outlier for a box plot?
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Outside the lower or upper fence. Those between the fence and the box are suspect.
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What constitutes an outlier for a Z-score?
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More than 3 standard deviations from the mean.
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In probability, what is an experiment.
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An experiment is a defined set of actions and outcomes.
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What is a _simple_ event?
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A simple event is one observation within an experiment.
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What is the sample space?
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The set of observations that can be made during the experiment
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What is an event?
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A set of related simple events.
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How do you calculate the probability of an event?
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Identify the experiment, the sample space, the simple events, assign probability of each simple event. Event probabilities are the sum of the simple events associated with them.
Outcomes of A / total outcomes |
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Describe the union of two events..
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The probability that either one or both of the events will occur.
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Describe the intersection of two events...
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The probability that both events, e.g. A AND B will occur.
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Describe the complement of an event probability...
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The sum of the complement of an event and the event itself is 1, so 1 - the event is its complement.
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What is the conditional probability that A occurs if B has already occurred?
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P(A|B) is P(A AND B)/P(B)
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What does it mean if A and B are mutually exclusive?
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It means that A intersected with B has no simple events in common. A intersect B is the empty set.
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What does it mean if
P(A|B) = P(A)? |
It means that events A and B are are independent...
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What does it mean if P(B|A) != P(B)?
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It means that events A and B are dependent.
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What is the multiplicative rule for independent events?
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The multiplicative rule says that if A and B are independent, then A intersect B is P(A)P(B)
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How do you calculate the intersection of two events?
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P(A intersect B) is P(A|B)P(B)
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Describe the additive rule for mutually exclusive events...
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The additive rule says that if events A or B are mutually exclusive,
P(A union B) is P(A) + P(B) |
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How do you calculate the union of two events?
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P(A union B) is
P(A) + P(B) - P(A intersect B) |
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What is the purpose of Bayes rule?
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Bayes rule allows us to calculate an unknown conditional probability into a known one, e.g. if we want P(A|B) and have P(B|A).
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Describe the setup for Bayes law...
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P(A1..An)|B) =
P(B|A)P(B) / (P(B1)+P(B2)+P(Bn) |
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What are partitions of a data set?
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This is a method for distributing n items over b bins of k size. N!/((k!)(k2!)(k3!))
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What are combinations?
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The number of different selections of k items from a pool of p items. Order doesn't matter.
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What are permutations?
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The number of different selections of k items from p items. Order does matter.
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If you have 3 microprocessors, two compilers and three vendors, what is the rule you use to figure out how many ways you can make one selection from each?
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The multiplicative rule:
3*2*3 |
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What is 0! (factorial)
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1
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What is the difference between discrete data and continuous data?
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Discrete data also known as attribute data is exact. For example, on/off, defective/nondefective, or a count of items. Continuous data is pressure, volume, distance, temperature.
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Define univariate, bivariate, multivariate.
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Univariate means one variable; bivariate, two; multivariate, several
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Describe the empirical rule for a normal distribution?
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68% of the data within 1 std dev. 95% within 2.
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How do you break a sample set into quartiles? percentiles?
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25/100*(n+1), round up
75/100*(n+1), round down 95/100*(n+1) |
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Describe inferential statistics...
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Using sample of a population to infer information about the whole.
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How do you handle probabilities in parallel?
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Parallel operations are unions and use 'OR'. You use the additive rule on these probabilities.
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How do you handle serial probabilities?
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Serial operations are intersections and use 'AND'. You use the multiplicative rule on these probabilities.
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