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denis23 [38]
3 years ago
13

Problem: According www.textrequest, an American between 18-24 sends and receives about 128 text messages per day. Assume that th

e population standard deviation is 30 for this age group. To get an idea about the true population mean you take a survey of 100 adults in that age group and find that their average is 135. Create a 90% confidence interval for the population average for this age group.
Mathematics
1 answer:
borishaifa [10]3 years ago
8 0

Answer:

(130.08, 139.92)

Step-by-step explanation:

Given that:

Mean (m) = 135

Standard deviation (σ) = 30

Sample size (n) = 100

α = 90%

The confidence interval value is obtained using the relation:

Mean ± Zcritical * (standard deviation / sqrt(n))

Zcritical at 90% = 1.64

standard deviation / sqrt(n) = 30 / sqrt(100)

= 30 / 10 = 3

Hence,

135 ± 1.64 * (3)

Lower limit : 135 - (1.64 * 3) = 130.08

Upper limit : 135 + (1.64 * 3) = 139.92

Hence,

Confidence interval = (130.08, 139.92)

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Find the ratio of the area inside the square but outside the circle to the area of the square in the picture
Eduardwww [97]

Answer:

0.2146

Step-by-step explanation:

From the picture:

The radius of the circle = r. This means that the area of the circle = πr²

Also For the square, the length of the square = 2r, Therefore the area of the square = Length × length = 2r × 2r = 4r²

The area inside the square but outside the circle = Area of square - Area of circle = 4r² - πr² = r²(4 - π) = 0.8584r²

The ratio of the area inside the square but outside the circle to the area of the square =  r²(4 - π) / 4r² = (4 - π) / 4 = 1 - π/4 = 0.2146

5 0
3 years ago
PLEASE HELP ASAP!!! CORRECT ANSWER ONLY PLEASE!!!
Kitty [74]

Answer:   (-2, 5) and (2, -3)

<u>Step-by-step explanation:</u>

Graph the line y = -2x + 1 (which is in y = mx + b format) by plotting the y-intercept (b = 1) on the y-axis and then using the slope (m = -2) to plot the second point by going down 2 and right 1 unit from the first point:

        y - intercept = (0, 1)            2nd point = ( -1, 1).

Graph the parabola y = x² - 2x - 3 by first plotting the vertex and then plotting the y-intercept (or some other point):

y = x^2-2x-3\quad \rightarrow \quad a=1,\ b=-2,\ c=-3\\\\\text{axis of symmetry:}\ x = \dfrac{-b}{2a}\ \longrightarrow \ x=\dfrac{-(-2)}{2(1)}=\dfrac{2}{2}=1\\\\\text{y-value of vertex:}\ f(1) = (1)^2-2(1)-3\quad \longrightarrow \quad y = 1 - 2 - 3=-4\\\\\text{y-intercept:}\ f(0)= (0)^2-2(0)-3\ \longrightarrow \ y=0 - 0 - 3 = -3 \\

         vertex = (1, -4)                2nd point (y-intercept) = (0, -3)


<em>see attached</em> - the graphs intersect at two points:  (-2, 5) and (2, -3)


8 0
3 years ago
What is 0.31 rounded to the nearest tenth
Tomtit [17]

0.31 rounded to the nearest tenth would be 0.3

This Chart should help you in the future:

8 0
3 years ago
A TV report conducted a survey of 947 people in New York City and found that 35% of the population believe that the Yankees will
garik1379 [7]

Answer:

35\% represents the sample proportion of the population

Step-by-step explanation:

From the question we are told that

   The sample size is  n  = 947

   The proportion of the population that believes that the Yankees will miss the playoffs this year is    k = 35\% = 0.35

From the question we are told the confidence level is  97%

   The lower limit of the confidence level is a = 28%

    The upper limit of the  b = 42%

Generally the sample proportion of this population is mathematically represented as

         \^ p = \frac{a+ b}{2}

=>      \^ p = \frac{28 + 42 }{2}

=>      \^ p = 35\%

Hence  35\% represents the sample proportion

8 0
3 years ago
Simplify , You may leave the numerator and denominator of your answer in factored form ?
ch4aika [34]
For this fraction, we have (3x+2) in both the numerator and the denominator. So, they will be cancelled together.
Then we can notice that we can divide the coefficients in the numerator and the denominator by 9 as 36/9 = 4 and 9/9 = 1

So, the expression now becomes:
(x+7) / 4(x-5) which is the simplest form.
8 0
4 years ago
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