Solve each system of linear equations by substitutions. X+2y =6 x-y=3

A clinical trial tests a method designed to increase the probability of conceiving a girl. In the study 400 babies were born, a

Masja [62]

Answer:

(a) 99% confidence interval for the percentage of girls born is [0.804 , 0.896].

(b) Yes, the proportion of girls is significantly different from 0.50.

Step-by-step explanation:

We are given that a clinical trial tests a method designed to increase the probability of conceiving a girl.

In the study 400 babies were born, and 340 of them were girls.

(a) Firstly, the pivotal quantity for 99% confidence interval for the population proportion is given by;

P.Q. = $\frac{\hat p-p}{\sqrt{\frac{\hat p(1-\hat p)}{n} } }$ ~ N(0,1)

where, $\hat p$ = sample proportion of girls born = $\frac{340}{400}$ = 0.85

n = sample of babies = 400

p = population percentage of girls born

Here for constructing 99% confidence interval we have used One-sample z proportion statistics.

So, 99% confidence interval for the population proportion, p is ;

P(-2.58 < N(0,1) < 2.58) = 0.99 {As the critical value of z at 0.5% level

of significance are -2.58 & 2.58}

P(-2.58 < $\frac{\hat p-p}{\sqrt{\frac{\hat p(1-\hat p)}{n} } }$ < 2.58) = 0.99

P( $-2.58 \times {\sqrt{\frac{\hat p(1-\hat p)}{n} } }$ < ${\hat p-p}$ < $2.58 \times {\sqrt{\frac{\hat p(1-\hat p)}{n} } }$ ) = 0.99

P( $\hat p-2.58 \times {\sqrt{\frac{\hat p(1-\hat p)}{n} } }$ < p < $\hat p+2.58 \times {\sqrt{\frac{\hat p(1-\hat p)}{n} } }$ ) = 0.99

99% confidence interval for p = [ $\hat p-2.58 \times {\sqrt{\frac{\hat p(1-\hat p)}{n} } }$ , $\hat p+2.58 \times {\sqrt{\frac{\hat p(1-\hat p)}{n} } }$ ]

= [ $0.85-2.58 \times {\sqrt{\frac{0.85(1-0.85)}{400} } }$ , $0.85+2.58 \times {\sqrt{\frac{0.85(1-0.85)}{400} } }$ ]

= [0.804 , 0.896]

Therefore, 99% confidence interval for the percentage of girls born is [0.804 , 0.896].

(b) Let p = population proportion of girls born.

So, Null Hypothesis, $H_0$ : p = 0.50 {means that the proportion of girls is equal to 0.50}

Alternate Hypothesis, $H_A$ : p $\neq$ 0.50 {means that the proportion of girls is significantly different from 0.50}

The test statistics that will be used here is One-sample z proportion test statistics;

T.S. = $\frac{\hat p-p}{\sqrt{\frac{\hat p(1-\hat p)}{n} } }$ ~ N(0,1)

where, $\hat p$ = sample proportion of girls born = $\frac{340}{400}$ = 0.85

n = sample of babies = 400

So, the test statistics = $\frac{0.85-0.50}{\sqrt{\frac{0.85(1-0.85)}{400} } }$

= 19.604

Now, at 0.01 significance level, the z table gives critical value of 2.3263 for right tailed test. Since our test statistics is way more than the critical value of z as 19.604 > 2.3263, so we have sufficient evidence to reject our null hypothesis due to which we reject our null hypothesis.

Therefore, we conclude that the proportion of girls is significantly different from 0.50.

8 0

3 years ago

A 36-foot-tall tree casts a 9-foot shadow. How tall is a nearby tree that casts a 14-foot shadow at the same time?

kiruha [24]

Answer:

Proportion states that the two fractions or ratios are equal.

Given the statement: A 36-foot-tall tree casts a 9-foot shadow.

To find the height of the nearby tree that cast a 14 foot shadow at the same time.

Let x be the height of the nearby tree.

By definition of proportion;

$\frac{\text{Height of thetall tree}}{\text{Shadow of the tall tree}} =\frac{\text{Height of the nearby tree}}{\text{Shadow of the nearby tree}}$

Substitute the given values we get;

$\frac{36}{9}=\frac{x}{14}$

Simplify:

$4 = \frac{x}{14}$

Multiply both sides by 14 we get;

$x= 4 \times 14 = 56$ foot.

therefore, the height of the nearby tree is, 56 foot.

7 0

3 years ago

A cylindrical can and a cone-shaped paper cup have the same radius and weight. If you use the cone to fill the van with water ho

Marta_Voda [28]

Answer:

3 cones

Step-by-step explanation:

It is given that there is a cylindrical shaped can and also a coned shaped paper cup. The radius and height of both the cylindrical can and the cone shaped paper cup are same.

So when we fill the cylindrical can with the full coned paper cup, it will take three cones of the paper cup to fill the can with water. This because the volume of a cone is $\text{one-third}$ of the volume of a cylinder that have the same base radius and height.