SOLUTION:
Step 1:
In this question, we are given the following:
Step 2:
A.) State the random variable:
X= the number of heads observed when you flip a coin three times
Step 3:
B.) construct a probability distribution table for the number of heads obtained over three tosses. Enter the X values from smallest to largest:
X P(X)
0 1/8
1 3/8
2 3/8
3 1/8
Step 4:
C.) Determine the shape of the probability distribution of x
- symmetric
Step 5:
D.) find the MEAN number of heads for this distribution
[tex]\begin{gathered} Mean\text{= ( 0 X }\frac{1}{8})\text{ + ( 1 x }\frac{3}{8})\text{ + ( 2 x }\frac{3}{8})\text{ + (3 x }\frac{1}{8}) \\ \text{Mean = 0+ }\frac{3}{8}+\frac{6}{8}+\frac{3}{8} \\ \text{Mean = }\frac{12}{8} \\ \text{Mean = 1. 5} \end{gathered}[/tex]
Step 6:
E.) find the standard deviation for the number of heads for this distribution:
[tex]S\tan dard\text{ Deviation = }\sqrt[]{(x\text{ -}\mu)^2\text{ P ( X = x )}}[/tex][tex]\begin{gathered} \sin ce\text{ }\mu\text{ = 1. 5, then we have that:} \\ \sqrt[]{\lbrack(0-1.5)^2X\text{ }\frac{1}{8}\rbrack+\lbrack(1\text{ - }1.5)^2\text{X }\frac{3}{8}\rbrack+\lbrack(2-1.5)^2}X\frac{3}{8}\rbrack+\lbrack(3-1.5)^2\text{ X }\frac{1}{8} \end{gathered}[/tex][tex]\begin{gathered} \sqrt[]{(2.\text{ 25 X }\frac{1}{8})\text{ + ( 0.25 X }\frac{3}{8})\text{ + ( 0. 25 X }\frac{3}{8})\text{ + (2.25 X }\frac{1}{8})} \\ =\text{ }\sqrt[]{0.28125+\text{ 0.09375 + 0.09375 + 0.28125}} \\ =\sqrt[]{0.75} \\ =0.866\text{ ( 3 decimal places)} \end{gathered}[/tex]
Step 7:
F.) find the probability of obtaining two or less heads over three tosses of a coin
[tex]P\text{ ( obtaining two or less heads) = }\frac{3}{8}+\text{ }\frac{3}{8}+\frac{1}{8}\text{ = }\frac{7}{8}[/tex]
