# Questions tagged [rule-of-thumb]

Advises on statistical analysis that are often useful in practice (but are not always guaranteed to work).

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### How small is too small to fit a reasonable long memory model?

When looking at papers about long memory they tend to analyze data sets whose length is in the thousands, see http://www.math.canterbury.ac.nz/~m.reale/pub/Reaetal2011.pdf for an example. My question ...
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### How should I treat categorical variables for the purpose of the “One in 10 rule”?

Hope a basic question like this is alright! To avoid overfitting, we try to maintain enough cases for the least common event per explanatory variable; people usually recommend at least 10. How should ...
1answer
356 views

### Equality of variances based on Rule of Thumb (for very small groups)

I have three groups with very small sample sizes (6 obs per each group). In order to use ANOVA I just want to make sure that the equality of variances is satisfied, as Levene's test does not have ...
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### How does one formalize a prior probability distribution? Are there rules of thumb or tips one should use?

While I like to think I have good grasp of the concept of prior information in Bayesian statistical analysis and decision making, I often have trouble wrapping my head around its application. I have ...
1answer
751 views

### Rule of thumb for the number of significant digits to report

What is a good rule of thumb for the number of significant digits to report? Preferably, the rule of thumb is given in a citable publication. I am particularly interested in a rule that does not ...
1answer
2k views

### How to tell a coefficient of variation (C.V.) is high?

I have a group of data series which contain hundreds of values. I've calculated the C.V.s of these data series, but I don't know how I can recognise if they are high or low according to the C.V. ...
2answers
859 views

### Rule of thumb for using logarithmic scale

When I am given a variable, I usually decide whether to take its logarithm based on gut feeling. Usually I base it on its distribution - if it has long tail (like: salaries, GDP, ...) I use logarithms....
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145 views

### How do “stacked” repeated samples influence our rules of thumb for minimum samples size in regression?

A professor in one of my graduate statistics courses once said, when briefly reviewing simple linear regression: "I would never EVER fit a line to fewer than 8-10 data points, it would make me feel......
1answer
7k views

### Optimal number of bins in histogram by the Freedman–Diaconis rule: difference between theoretical rate and actual number

Wikipedia reports that under the Freedman and Diaconis rule, the optimal number of bins in an histogram, $k$ should grow as $$k\sim n^{1/3}$$ where $n$ is the sample size. However, If you look at ...
3answers
875 views

### How strongly supported is a conclusion drawn from the correlation of 10 observations?

The Spearman’s rank correlation coefficient calculated for these observations is 0.826 (p<0.005). Is there something like a "rule of thumb" minimum number of observations?
2answers
24k views

### “When to use boxplot and when barplot” rules (of thumb?)

Both box-and-whisker plot and bar chart are appropriate graphics for ANOVA according to The R Book (Crawley, 2013), but which is more appropriate? I suppose it depends on situation... can anybody help ...
3answers
720 views

### Is there a simple method to calculate the minimum number of datalines needed for a machine learning algorithm with x variables?

Here is the problem: I am making a machine learning algorithm that takes the inputs and outputs of some software I've written, and I don't know how many datalines to produce to get results that are a '...
2answers
173 views

### Rule of thumb when drawing N samples from a discrete distribution with N possible values with replacement

I'm looking for an explanation and possibly the name of a rule of thumb: When drawing N samples with replacement from a discrete uniform distribution of N values, it is very likely that: 1/3 of the ...
3answers
2k views

### Minimum items for questionnaire

Is there a minimum item for questionnaire? Some researchers said that the total items for teenagers ranging from 80-110 items
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### Min-max vs. standard deviation when plotting error bars

I am running some experiments in which I plot the values of some variable y (averaged over 4 runs) against some independent variable x. I also compare the effect of z. In other words: horizontal axis:...
1answer
5k views

### Histogram with uniform vs non-uniform Bins

This question describes the basic difference between a uniform and a nonuniform histogram. And this question discusses the rule of thumb for picking the number of bins of a uniform histogram that ...
1answer
255 views

### Is Rule of Three inappropriate in some cases?

I'm building binomial proportion confidence intervals for a patient dataset containing the frequency of home nursing visits during the week prior to hospital admission. The freq. of home visit ...
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### Rule of thumb - number of predictors - Poisson regression rates

I am interested in estimating a Poisson regression for mortality rates, with number of deaths as the dependent variable and log(population size) as the offset. I have 50 observations (states). I am ...
2answers
1k views

### Rules of Thumb to choose an initial number of class intervals and refine that choice (potentially automatically)

I was wondering if there are established rules of thumb (or algorithms) that, given a set of observations can help: choose an initial number of class intervals. refine that choice to a better number. ...
1answer
6k views

### How to decide which decision tree classifier to use?

I am confused about which decision tree algorithm in weka to use for my application. I have 5 real input variables and 2 classes. In various online tutorials J48 (C 4.5) seems to be the algorithm of ...
1answer
2k views

### Basic easy rules for statistics

In a binomial experiment, if we observe $x=0$ positive individual among $n$ individuals, then the proportion of positive individuals is significantly lower than $3/n$ with a type 1 error less than and ...
2answers
452 views

### Effect size interpretation

If r between X and Y is 0.74, then r-squared is 55%. According to many 'rules of thumb' and others, the effect size (in this case r) is considered 'moderate' or 'medium'. As such, only 55% of the ...
2answers
628 views

### Good online resource with tips on graphing association between two numeric variables under various conditions

Context: Over the while I've acquired a set of heuristics on how to effectively plot the association between two numeric variables. I imagine most people who work with data would have a similar set ...
3answers
741 views

### $L_1$ or $L_.5$ metrics for clustering?

Does anyone use the $L_1$ or $L_.5$ metrics for clustering, rather than $L_2$ ? Aggarwal et al., On the surprising behavior of distance metrics in high dimensional space said (in 2001) that $L_1$ ...
7answers
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### Rules of thumb for minimum sample size for multiple regression

Within the context of a research proposal in the social sciences, I was asked the following question: I have always gone by 100 + m (where m is the number of predictors) when determining ...
1answer
719 views

### Sample size required to determine which of a set of advertisements has the highest click through rate

I am a software designer by trade and I am working on a project for a client, and I would like to make sure that my analysis is statistically sound. Consider the following: We have n advertisements (...
2answers
5k views

### When to use Equal-Frequency-Histograms

... instead of e.g. the popular Equal-Width-Histograms. Additional question: What is a good/robust rule of the thumb to calculate the number of bins for equal frequency histograms (like the ...
4answers
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### MANOVA and correlations between dependent variables: how strong is too strong?

The dependent variables in a MANOVA should not be "too strongly correlated". But how strong a correlation is too strong? It would be interesting to get people's opinions on this issue. For instance, ...
24answers
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### Rules of thumb for “modern” statistics

I like G van Belle's book on Statistical Rules of Thumb, and to a lesser extent Common Errors in Statistics (and How to Avoid Them) from Phillip I Good and James W. Hardin. They address common ...
4answers
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### What references should be cited to support using 30 as a large enough sample size?

I have read/heard many times that the sample size of at least 30 units is considered as "large sample" (normality assumptions of means usually approximately holds due to the CLT, ...). Therefore, in ...
8answers
156k views

### Calculating optimal number of bins in a histogram

I'm interested in finding as optimal of a method as I can for determining how many bins I should use in a histogram. My data should range from 30 to 350 objects at most, and in particular I'm trying ...