Statistics: what percent of marriages last 25 years?
Self-tutoring about statistics: the tutor asks a question. What percent of marriages last 25 years? Thirty-five percent, apparently. That’s in the US, 2011. Source: census.gov
Category: statistics
Statistics: endogeneity
Tutoring statistics, definitions are of interest. The tutor mentions endogeneity. endogeneity: when an explanatory variable affects the error term in a predictable way. An example would be a model that measures the amount of daily sunlight received, but assumes (wrongly) …
Statistics: rarefaction curve
Self-tutoring about statistics: the tutor mentions rarefaction. I’ve seen the terms rarefy, rarefied, rarefaction, etc, but never knew what they meant. Today I decided to change that, but it was like opening an overfilled closet where everything jumps out at …
Statistics: base rate fallacy, part 2: belief vs disbelief
Tutoring statistics, so many inroads are available. The tutor continues about the base rate fallacy. Continuing from my post yesterday, I’ll explore a connection to it: believing what you see, vs not. The base rate fallacy means that people believe …
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Statistics: base rate fallacy, part 1: false-positive paradox
Tutoring statistics, you encounter day-to-day ideas. The tutor mentions the false-positive paradox. false-positive paradox: In a population where condition A is extremely uncommon, most tests for it that yield “positive” may likely be false. The false-positive paradox is easy to …
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Statistics: the 68-95-99 rule
Tutoring statistics, rules of thumb can be key. The tutor mentions a real-life application of the 68-95-99 rule. With hot, dry weather comes also the job of irrigation, for those who choose to do so. My wife wants a nice …
Tagged with: standard deviation of sprinkler reach
Statistics: how often can something “better” be expected to perform better?
Tutoring statistics, you might imagine everyday situations. The tutor brings up one. Let’s imagine we have two mile runners. Runner 1, called R1, has mean time 4:45, with standard deviation 10s; R2 has mean time 5:00 with standard deviation 12s. …
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Spreadsheets: p-value with Excel
Tutoring stats, you deal with p-values. The tutor shows an Excel connection. In my posts here and here I mention p-values. Example: Using Excel, get a two-tailed p-value for z=2.4 Solution: Using symmetry, it’s best to get the cumulative z-probability …
Tagged with: p-value using excel
Statistics: Ten facts about the chi-square distribution
Tutoring statistics, distributions are of constant interest. The tutor brings up ten points about the chi-square distribution. The chi-square distribution may not be discussed much in a first-level stats course. It’s used to estimate or evaluate variance, rather than central …
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Statistics: an assumption of the linear regression model
Tutoring statistics, linear regression is perennial. The tutor mentions an assumption it includes. When appropriate, linear regression models data by the equation y = a + bx + e, e being an error term due to variability. An inherent assumption …
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