We read your photo as:

At each turn in a game a player score is denoted by x is found as follows players throw a fair six sided die once and if the number showing on the die is 4,5,6 that number is the value of X if the number shows an 1,2,3 then the thrower throws the die again and x is the number showing on the second throw probability distribution of x is shown in the following terms

Mathematics

ScanSolve AI Answer

Answers

3 parts
a

P(X=6)=14P(X=6) = \frac{1}{4}

b

E(X)=174E(X) = \frac{17}{4}

Var(X)=11348Var(X) = \frac{113}{48}

c

P(Xˉ>4)≈0.9894P(\bar{X} > 4) \approx 0.9894

Step-by-step solution

9 steps

The problem describes a game where a player's score XX is determined by rolling a fair six-sided die.

  • If the first roll is 4, 5, or 6, XX is that number.
  • If the first roll is 1, 2, or 3, the die is rolled again, and XX is the number on the second roll.

The probability distribution of XX is given in the table:

X123456P(X=x)112112112141414\begin{array}{|c|c|c|c|c|c|c|} \hline X & 1 & 2 & 3 & 4 & 5 & 6 \\ \hline P(X=x) & \frac{1}{12} & \frac{1}{12} & \frac{1}{12} & \frac{1}{4} & \frac{1}{4} & \frac{1}{4} \\ \hline \end{array}

Part a· 2 steps

Show how the result P(X=6)=1/4P(X=6) = 1/4 is obtained.

  1. Identify the ways to score X=6X=6.

    There are two scenarios for X=6X=6:

    1. The first roll is a 6. The probability of this is P(first roll is 6)=16P(\text{first roll is 6}) = \frac{1}{6}.
    2. The first roll is 1, 2, or 3 (probability 36=12\frac{3}{6} = \frac{1}{2}), AND the second roll is a 6 (probability 16\frac{1}{6}). The probability of this sequence is P(first roll is 1,2,3)×P(second roll is 6)=12×16=112P(\text{first roll is 1,2,3}) \times P(\text{second roll is 6}) = \frac{1}{2} \times \frac{1}{6} = \frac{1}{12}.
  2. Sum the probabilities of these mutually exclusive scenarios.

    P(X=6)=P(first roll is 6)+P(first roll is 1,2,3 and second roll is 6)P(X=6) = P(\text{first roll is 6}) + P(\text{first roll is 1,2,3 and second roll is 6}) P(X=6)=16+112P(X=6) = \frac{1}{6} + \frac{1}{12} P(X=6)=212+112P(X=6) = \frac{2}{12} + \frac{1}{12} P(X=6)=312P(X=6) = \frac{3}{12} P(X=6)=14\boxed{P(X=6) = \frac{1}{4}}

Part b

E(X)=174E(X) = \frac{17}{4}

Find E(X)E(X) and show that Var(X)=118/48Var(X) = 118/48.

  1. Calculate the expected value E(X)E(X).

    E(X)=∑xP(X=x)E(X) = \sum x P(X=x) E(X)=1(112)+2(112)+3(112)+4(14)+5(14)+6(14)E(X) = 1\left(\frac{1}{12}\right) + 2\left(\frac{1}{12}\right) + 3\left(\frac{1}{12}\right) + 4\left(\frac{1}{4}\right) + 5\left(\frac{1}{4}\right) + 6\left(\frac{1}{4}\right) E(X)=1+2+312+4+5+64E(X) = \frac{1+2+3}{12} + \frac{4+5+6}{4} E(X)=612+154E(X) = \frac{6}{12} + \frac{15}{4} E(X)=12+154E(X) = \frac{1}{2} + \frac{15}{4} E(X)=24+154E(X) = \frac{2}{4} + \frac{15}{4} E(X)=174\boxed{E(X) = \frac{17}{4}}
  2. Calculate E(X2)E(X^2).

    E(X2)=∑x2P(X=x)E(X^2) = \sum x^2 P(X=x) E(X2)=12(112)+22(112)+32(112)+42(14)+52(14)+62(14)E(X^2) = 1^2\left(\frac{1}{12}\right) + 2^2\left(\frac{1}{12}\right) + 3^2\left(\frac{1}{12}\right) + 4^2\left(\frac{1}{4}\right) + 5^2\left(\frac{1}{4}\right) + 6^2\left(\frac{1}{4}\right) E(X2)=1+4+912+16+25+364E(X^2) = \frac{1+4+9}{12} + \frac{16+25+36}{4} E(X2)=1412+774E(X^2) = \frac{14}{12} + \frac{77}{4} E(X2)=76+774E(X^2) = \frac{7}{6} + \frac{77}{4}

    To combine, use a common denominator of 12:

    E(X2)=7×212+77×312E(X^2) = \frac{7 \times 2}{12} + \frac{77 \times 3}{12} E(X2)=1412+23112E(X^2) = \frac{14}{12} + \frac{231}{12} E(X2)=24512E(X^2) = \frac{245}{12}
  3. Calculate the variance Var(X)Var(X).

    Var(X)=E(X2)−(E(X))2Var(X) = E(X^2) - (E(X))^2 Var(X)=24512−(174)2Var(X) = \frac{245}{12} - \left(\frac{17}{4}\right)^2 Var(X)=24512−28916Var(X) = \frac{245}{12} - \frac{289}{16}

    To subtract, use a common denominator of 48:

    Var(X)=245×448−289×348Var(X) = \frac{245 \times 4}{48} - \frac{289 \times 3}{48} Var(X)=98048−86748Var(X) = \frac{980}{48} - \frac{867}{48} Var(X)=11348Var(X) = \frac{113}{48}

    Note: The problem asks to show that Var(X)=118/48Var(X) = 118/48. Based on the given probability distribution and game rules, the calculated variance is 113/48\mathbf{113/48}. There appears to be a typo in the problem statement's expected variance value.

    Var(X)=11348\boxed{Var(X) = \frac{113}{48}}

Part c

P(Xˉ>4)≈0.9894P(\bar{X} > 4) \approx 0.9894

A sample of 200 values of XX is denoted by Xˉ\bar{X}. Use the Central Limit Theorem to estimate P(Xˉ>4)P(\bar{X} > 4).

  1. Identify the population parameters for XX.

    From part (b):
    Population mean, μ=E(X)=174=4.25\mu = E(X) = \frac{17}{4} = 4.25
    Population variance, σ2=Var(X)=11348\sigma^2 = Var(X) = \frac{113}{48}
    Population standard deviation, σ=11348≈1.534336\sigma = \sqrt{\frac{113}{48}} \approx 1.534336

  2. Apply the Central Limit Theorem (CLT).

    For a large sample size (n=200n=200), the sample mean Xˉ\bar{X} is approximately normally distributed with:
    Mean of sample means, μXˉ=μ=4.25\mu_{\bar{X}} = \mu = 4.25
    Standard deviation of sample means (standard error), σXˉ=σn\sigma_{\bar{X}} = \frac{\sigma}{\sqrt{n}}

    σXˉ=11348200=11348×200=1139600\sigma_{\bar{X}} = \frac{\sqrt{\frac{113}{48}}}{\sqrt{200}} = \sqrt{\frac{113}{48 \times 200}} = \sqrt{\frac{113}{9600}} σXˉ≈0.011770833≈0.1084935\sigma_{\bar{X}} \approx \sqrt{0.011770833} \approx 0.1084935
  3. Standardize Xˉ\bar{X} to a z-score.

    We want to estimate P(Xˉ>4)P(\bar{X} > 4).

    Z=Xˉ−μXˉσXˉZ = \frac{\bar{X} - \mu_{\bar{X}}}{\sigma_{\bar{X}}} Z=4−4.250.1084935Z = \frac{4 - 4.25}{0.1084935} Z=−0.250.1084935Z = \frac{-0.25}{0.1084935} Z≈−2.3043Z \approx -2.3043
  4. Find the probability using the standard normal distribution.

    We need to find P(Z>−2.3043)P(Z > -2.3043).
    Using a standard normal distribution table or calculator:

    P(Z>−2.3043)=1−P(Z≤−2.3043)P(Z > -2.3043) = 1 - P(Z \le -2.3043) P(Z≤−2.3043)≈0.0106P(Z \le -2.3043) \approx 0.0106 P(Z>−2.3043)≈1−0.0106P(Z > -2.3043) \approx 1 - 0.0106 P(Xˉ>4)≈0.9894\boxed{P(\bar{X} > 4) \approx 0.9894}
Was this helpful?

Try one yourself

A new problem that tests the same skill.

Still stuck on this one?

Ask a follow-up, and the answer starts from this question.

Got a different question?Ask your own question