# Tagged Questions

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### What is the purpose of the standard deviation?

I don't have any knowledge of statistics beyond high school common sense. Why is the standard deviation usually seen in combinatorics textbooks, and why is the standard deviation defined ...
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### How did Target figure out a teen girl was pregnant before her father did?

First of all I do not have a mathematics degree only a B.S. in finance so please take that into account when writing an answer. Generally what type of mathematics is involved here? And specifically ...
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### z-interval and sample size what is a normal sample size

Can a Z-interval be used when the sample size is between 15-30? does the variable play a role? I'm not too sure if it makes a difference. I know it can be used if the population is a normal or large ...
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### A theorem about inductive inference

In the book 'Introduction of the theory of Statistics' by Mood,Graybill,Boes (third edition)on page 220 (Chapter 6 on Sampling) you can read: 'Inductive inference is well known to be a hazardous ...
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### Single number to represent a ratio?

There's probably a very simple answer to this, but I can't put my finger on it. I have two numbers. I want one to be large, and the other to be small. I'd like to identify these with a single ...
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### What is the deepest / most interesting known connection between Trigonometry and Statistics?

I'm teaching both at the same time to different classes in high school, so I just wondered about this. Added by OP on 16.May.2011 (Beijing time) I mean Statistics only, without Probability. In ...
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### Calculate relative contribution to percent change

Let me use a simple example to illustrate my problem. First, assume we are calculating rate r at time t such that rt = xt / yt. Furthermore, each measure has two component parts: X = xa + xb and Y = ...
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### Is the above statement true for maths?

In maths, you can use something as simple as statistical analysis to intuit the theory, and in comp-science you can use simulators. Is the above statement true for maths ?