## Your Questions About Odds Calculator

Chris asks…

## Could andyone tell me how to write a program on my Ti-83 plus calculator that says if a number is prime or not?

I made one that tells you if the number is odd or even but how could I make one that says if it is prime?

### admin answers:

Here’s one I’m just making up on the spot, so I can’t guarantee the accuracy of the program, but it should work:

Prompt N

For(C,2,√(N

If N=Cint(N/C

Then

Disp „COMPOSITE

Stop

End

End

Disp „PRIME

Thomas asks…

## Can you view a website’s Perl scripts?

I have found a website that runs a Perl script as part of an **odds** **calculator**. I want to see the Perl script so that I can better understand the formula they’re using. Is there any way to view a website’s Perl script using Internet Explorer, other than „view source“ (which isn’t working in this case)?

### admin answers:

No you can not. The perl scripts are executed on the server (Server side code) and are never sent to the client (Browser). This is a security measure to protect the application. The web server will prevent browsing of the server side code files.

John asks…

## Calculating odds of failing?

Assume that a new electronic **calculator** has a probability of failure of 0.016. Find the **odds** of failing.

### admin answers:

Okay that is 1.6%

So the probablity of failing is 1.6/100

and the odds are 1.6:98.4

(100-1.6=98.4)

Donald asks…

## Weird calculator spits out odd answer?

Ok, my original question was http://answers.yahoo.com/question/index?qid=20090707115610AAHSO3U and I got my answer, but why when I put i^99 I get 4.9E-12-i and not -i?

### admin answers:

It’s just a calculation error.

4.9E-12 is VERY small for the calculator… Almost zero, even. The calculator ran an algorithm and made rounding errors at various steps, eventually giving us something VERY close to -i, but not exactly so.

The answer to i^99 is -i, though.

——

By the way, here is a likely way the calculator computes it (this could have some math you haven’t seen yet):

i = e^(pi/2 * i)

i^99 = e^(99pi/2 * i) = cos(99pi/2) + i * sin(99pi/2)

When you have the calculator (at least my TI-84) compute it, you find that it says

cos(99pi/2) = 4.9E-12

even though it actually is equal to 0.

The rounding error is in two places:

(1) computing 99pi/2

(2) Taking the cosine.

James asks…

## Statistics on the TI-89 graphics calculator?

Firstly, can someone please explain WHAT exactly IS the standard deviation?

And can someone please tell me how to find the standard deviation of a set of numbers using a TI-89?

I can find the „stdDev(“ function and to find the standard deviation of say the numbers 1, 4, 5, 5, 6, 7, 8 and 9, I assumed that you’d type this in:

stdDev(1,4,5,5,6,7,8,9)

But then when I hit ENTER it says „Error: Too many arguments“ and if I try to reduce the number of numbers then it says „Error: Data type“

I need to be able to find the standard deviation of many numbers at once (like around 20 since my maths book is… odd) with my **calculator** and I’m really stumped. My maths book only explains how to do it using TI-84 or 83 calculators which doesn’t really help me… Any help would be much appreciated!

### admin answers:

Enter the following:

{1, 2, 3, 4, 5, 6, 7, 8, 9} → x

stdDev(x)

OR

stdDev({1, 2, 3, 4, 5, 6, 7, 8, 9})

the stdDev function works with a list only.

The standard deviation is a measure of spread.

Think of the mean as the center or mass of the data

the Variance is the second moment, or the moment of inertia. The units of variance are the units squared of the data, e.g., if the data is in inches, then the variance is in inches^2. The squared units are not very useful to us in getting an idea about the spread of data. By taking the square root of the variance, the standard deviation, we have a meaningful and unit correct measure of spread.

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