Friday
August 1, 2014

Homework Help: Math

Posted by SherylA on Thursday, October 5, 2006 at 7:01pm.

*Sigh* Can someone explain to me how I would work thru this problem?

An honest coin tossed n=3600 times. Let the random variable Y denote the number of tails tossed.
(a) find the mean and the standard deviation of the distribution of the random variable Y
(b) what are the chances that Y will fall comewhere between 1770 and 1830?
(c) what are the chances that Y will fall somewhere between 1800 and 1830?
(d) what are the chances that Y will fall somewhere between 1830 and 1860?


By honest coin we mean one where P(H)=P(T)=.5 with H and T standing for heads and tails.
This is a Bernoulli trial with mean p=.5 variance = p(1-p)=.5^2=.25 and standard deviation = sqrt(variance)=.5
To answer (a) the expected number of tails is p*n where n is the number of tosses, so .5*3600 is E(#Tails). The s.d should still be .5 since that's the prob. of tails and heads.
For (b) P(1770<=X<=1830) so use P(X=x) where x is a number of trials. The prob. of P(x) = [n choose x]*(p^x)(1-p)^(n-x). The P(X<=1830)=1-P(1831) and P(1770<=X)=1-P(1771), so P(1770<=X<=1830) is P(1771) - P(1831).
Considering the size of the numbers you won't be able to evaluate them directly, unless you take the time to do some arithmetic.
Parts (c) and (d) are done similarly.

Answer this Question

First Name:
School Subject:
Answer:

Related Questions

statistics - air coin is flipped 20 times. a. Determine the probability that the...
math - When a coin is tossed four times, sixteen equally likely outcomes are ...
Math - When a coin is tossed four times, sixteen equally likely outcomes are ...
Statistics - Suppose Tori has an unfair coin which lands on Tails with ...
Math Problem ( 6th grade math) - Brandon tosses a coin 500 times. The coin lands...
probability - A fair coin is flipped independently until the first Heads is ...
Data Management - A random variable X is defined as the number of heads observed...
Probabilty - Biased coin has a 0.4 probability of landing on tails. The random ...
Math - Would you be more likely to get at least 70% tails if you flip a fair ...
MATH - PLEASE HELP - A biased coin is tossed 5 times where p(t) = .6. determine ...

Search
Members