Probability question

[rmccafferty]

Does anyone know how to set up this problem to solve it?

Four relatives are going to give you money for your birthday. The amount each relative gives you is equally likely to be any number between $0 and $200. The chance that the total amount of money you receive is at most $300 is _____?

 

[dispelthemyth]

FYI I'm no statistician


You could test it using Rand()*200 or randbetween(0,200) over x samples (although the debate about how random rand is reallly)

in cells A1:A10000 or whatever you want put (i went to 100,000)


Sheet1

*	A	B	C	D	E	F	G
Sample	Test	>= 300?	*	*	*	*
*	>300
*	<300	*
*	*	*	*
*	*	*	*
*	*	*	*

<tbody>
[TD="bgcolor: #cacaca, align: center"]1[/TD]

[TD="bgcolor: #cacaca, align: center"]2[/TD]
[TD="align: right"]1[/TD]
[TD="align: right"]387.289[/TD]
[TD="align: right"]1[/TD]

[TD="align: right"]79961[/TD]
[TD="align: right"]79.96%[/TD]

[TD="bgcolor: #cacaca, align: center"]3[/TD]
[TD="align: right"]2[/TD]
[TD="align: right"]265.551[/TD]
[TD="align: right"]0[/TD]

[TD="align: right"]100000[/TD]

[TD="bgcolor: #cacaca, align: center"]4[/TD]
[TD="align: right"]3[/TD]
[TD="align: right"]389.4927[/TD]
[TD="align: right"]1[/TD]

[TD="bgcolor: #cacaca, align: center"]5[/TD]
[TD="align: right"]4[/TD]
[TD="align: right"]427.6322[/TD]
[TD="align: right"]1[/TD]

[TD="bgcolor: #cacaca, align: center"]6[/TD]
[TD="align: right"]5[/TD]
[TD="align: right"]404.7658[/TD]
[TD="align: right"]1[/TD]

</tbody>

Spreadsheet Formulas

Cell Formula B2 =RAND()*200+RAND()*200+RAND()*200+RAND()*200 C2 =IF(B2<300, 0,1) F2 =SUM(C:C) G2 =F2/F3 B3 =RAND()*200+RAND()*200+RAND()*200+RAND()*200 <tbody> </tbody>

<tbody>
</tbody>

Excel tables to the web >> Excel Jeanie HTML 4

 

[shg]

See the same question and many answers at http://www.mrexcel.com/forum/excel-questions/695917-probability-tricky-question.html

 

[dispelthemyth]

Thanks for the link

Not being a statistician as i said earlier i got ~80%, seeing that thread it appears ~20% is popular, but that seems wrong from a basic maths point of view to me

20% = £40 per person, but if the ranges of values is £0 - £200 and no weighting given, the expectation per person is 50% @ £100 which indicates the answer should be > 50% over a large sample

See the same question and many answers at http://www.mrexcel.com/forum/excel-questions/695917-probability-tricky-question.html

 

[barry houdini]

Not being a statistician as i said earlier i got ~80%, seeing that thread it appears ~20% is popular, but that seems wrong from a basic maths point of view to me

I think your approach is fine but the question asks for

The chance that the total amount of money you receive is at most $300

. Your ~80% is the chance that it's more than $300, i.e. the opposite

 

[dispelthemyth]

Thanks i must have missed that "little" detail

~80% is the chance that it's more than $300, i.e. the opposite