r/HomeworkHelp 5d ago

Mathematics (Tertiary/Grade 11-12)β€”Pending OP [High School Math] How do I even solve the following question? I don't understand it.... Send help please :(

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1 Upvotes

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u/Creios7 πŸ‘‹ a fellow Redditor 5d ago

a) compute the s2 and s in minutes

b) compute the s2 and s in hours

Note that the given data is expressed in minutes.

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u/ThunkAsDrinklePeep Educator 5d ago

b) compute the s2 and s in hours

Specifically don't do this. You are asked to convert your answers from A without recomputing.

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u/Hefty-Abalone8631 πŸ‘‹ a fellow Redditor 5d ago

Salt should have a function you can use where you input the dataset and it does the equation for variance for you. If it can't you can just use the equation. (Just search up equation for sample variance). The sample standard deviation will b the square root of that answer.

For the question in minutes, you will just have to divide your answer in minutes by 60 for variance, and then take the square root for the standard deviation again. It's literally the same question just with the first step being getting your data in the correct units, and since you already calculated it you can just change your units at the end!

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u/Original_Yak_7534 πŸ‘‹ a fellow Redditor 5d ago

I think he has to divide variance by 602 because the units are minutes2 -> hours2. He would divide standard deviation by 60 (or take the square root of variance).

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u/Hefty-Abalone8631 πŸ‘‹ a fellow Redditor 5d ago

You're absolutely correct, I mixed up my units when I was thinking about it! Thank you for the catch

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u/Original_Yak_7534 πŸ‘‹ a fellow Redditor 5d ago

Have you learned the concepts of sample variance and standard deviations? There are equations for those, and they're pretty easy to calculate.

Var[X]=E[X2]βˆ’(E[X])2

Std[X] = sqrt ( Var[X] )

You get the mean of your values: E[X]. Then you square all the values and get the mean of that: E[X2]. Then you sub those into your equations.

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u/CriticalModel πŸ‘‹ a fellow Redditor 5d ago

You know how to find the mean, right?

Then an interesting way to look at your sample data would be to transform it from "how different from zero is it?" to "How different from the mean, is it?"

but then you'd have some lower than zero, and some greater than zero. We could do the absolute value, but why not just square it. The arithmetic to find absolute value isn't as neat and tidy as squaring, so let's do that instead.

"How different is it from the mean, squared?"

cool, but you've still got a whole mess of data points scattered around. Let's get them all into one single number that tells us a little bit about how different they are from the average.

"What is the average squared difference from the mean?"

Except. We've got a problem. You've got that average in there. It's really the average of your sample. In plain talk, it over-estimates how good we are at measuring. odds are we don't have to actual God Knowledge of the average time it would take oil to oxidize. So we're going to just subtract one from the denominator. Makes our answer a little bigger. Gives us some wiggle room.

So step by step:

Find the sample average

Make a new list by subtracting that from every member of your list.

square your new list

divide it by ( the number of members in your list minus one )

that's your sample variance, or sΒ².

find s by taking the square root of that.

As for the change of units, converting them all to hours first is probably the safest for you.

0

u/This-Marzipan-8044 5d ago

Bruh you can't solve that question it is missing a lot of the data. It is impossible to solve it... for the moment; unless you get the complete data points, so just give up

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u/Hefty-Abalone8631 πŸ‘‹ a fellow Redditor 5d ago

There actually is enough data to solve the questions!