Probability- hair treatment

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jcnissi: Junior | Next Rank: 30 Posts; Posts: 18; Joined: Sat Jun 12, 2010 10:17 pm; Thanked: 1 times

by jcnissi » Thu Nov 18, 2010 9:55 pm

I'm really good with math but unfortunately, statistics is my weakest point. I'm trying to do all sorts of statistic practice problems so that I can get better. Any help is greatly appreciated!

A particular hair treatment program has caused hair growth in 70% of its users. A random sample of 15 users is obtained. Using the Binomial Probability Distribution, determine the following probabilities:

a) That exactly 14 experienced hair growth.

b) That less than 9 experienced hair growth.

c) That more than 10 experience hair growth.

d) That 15 or more experience hair growth.

e) That 7 or less experienced hair growth.

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Source: Beat The GMAT — Problem Solving | Thu Nov 18, 2010 9:55 pm

karanrulz4ever: Master | Next Rank: 500 Posts; Posts: 358; Joined: Fri Jun 25, 2010 9:47 amFollowed by: 4 members; Location: Mumbai; Thanked: 34 times; GMAT Score:740

by karanrulz4ever » Fri Nov 26, 2010 10:15 pm

You do not have binomial probability questions in GMAT. If you are aiming for GMAT seriously, solve questions which have good chance of appearing on the GMAT test. Don't solve questions which have no chance of appearing.

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Night reader: Legendary Member; Posts: 1337; Joined: Sat Dec 27, 2008 6:29 pmFollowed by: 10 members; Thanked: 127 times

by Night reader » Fri Nov 26, 2010 10:43 pm

karanrulz4ever wrote:You do not have binomial probability questions in GMAT. If you are aiming for GMAT seriously, solve questions which have good chance of appearing on the GMAT test. Don't solve questions which have no chance of appearing.

I agree with Karan, knowing how to solve the chay square stats or f-parameter will not help too much on GMAT.

Once, I tried to solve a work problem with three variables and two equations here; it took me a while. I even had to grab some dusty complex math staff of my sophomore uni year. Trying hard to apply matrix and Gauss solutions, I ended up with parameters for the third variable. Don't waste your time on rocket science what fingers can find.

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goyalsau: Legendary Member; Posts: 866; Joined: Mon Aug 02, 2010 6:46 pm; Location: Gwalior, India; Thanked: 31 times

by goyalsau » Fri Nov 26, 2010 11:47 pm

jcnissi wrote:I'm really good with math but unfortunately, statistics is my weakest point. I'm trying to do all sorts of statistic practice problems so that I can get better. Any help is greatly appreciated!

A particular hair treatment program has caused hair growth in 70% of its users. A random sample of 15 users is obtained. Using the Binomial Probability Distribution, determine the following probabilities:

a) That exactly 14 experienced hair growth.

b) That less than 9 experienced hair growth.

c) That more than 10 experience hair growth.

d) That 15 or more experience hair growth.

e) That 7 or less experienced hair growth.

This is no way a Gmat question..............................

Saurabh Goyal
[email protected]
-------------------------

EveryBody Wants to Win But Nobody wants to prepare for Win.

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Matt@VeritasPrep: GMAT Instructor; Posts: 2630; Joined: Wed Sep 12, 2012 3:32 pmFollowed by: 119 members; Location: East Bay all the way; Thanked: 625 times; GMAT Score:780

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by Matt@VeritasPrep » Thu Oct 12, 2017 9:18 pm

Not sure how this one got on the front page, but I do this stuff for my day job a lot. Here's an R function I wrote that will answer all five parts:

hairfun <- function(a,b,p,x){sum(sapply(a:b, function(p, x, k){p^k * (1-p)^(x-k) * choose(x, k)}, p=p, x=x))}

where a = the minimum number you want, b = the maximum number you want, p = the probability of each trial, and x = the number of trials, and sapply is found in the dplyr package.

For example, the answer to (2) would be found by running hairfun(0, 8, .7, 15), and the answer to (1) would be hairfun(14, 14, .7, 15).

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