Heyyyyyy im back with another question =v=

The brand manager for a brand of toothpaste must plan a campaign designed to increase brand recognition. He wants to first deter

VMariaS [17]

Answer:

He must survey 123 adults.

Step-by-step explanation:

In a sample with a number n of people surveyed with a probability of a success of $\pi$ , and a confidence level of $1-\alpha$ , we have the following confidence interval of proportions.

$\pi \pm z\sqrt{\frac{\pi(1-\pi)}{n}}$

In which

z is the z-score that has a p-value of $1 - \frac{\alpha}{2}$ .

The margin of error is:

$M = z\sqrt{\frac{\pi(1-\pi)}{n}}$

Assume that a recent survey suggests that about 87% of adults have heard of the brand.

This means that $\pi = 0.87$

90% confidence level

So $\alpha = 0.1$ , z is the value of Z that has a p-value of $1 - \frac{0.1}{2} = 0.95$ , so $Z = 1.645$ .

How many adults must he survey in order to be 90% confident that his estimate is within five percentage points of the true population percentage?

This is n for which M = 0.05. So

$M = z\sqrt{\frac{\pi(1-\pi)}{n}}$

$0.05 = 1.645\sqrt{\frac{0.87*0.13}{n}}$

$0.05\sqrt{n} = 1.645\sqrt{0.87*0.13}$

$\sqrt{n} = \frac{1.645\sqrt{0.87*0.13}}{0.05}$

$(\sqrt{n})^2 = (\frac{1.645\sqrt{0.87*0.13}}{0.05})^2$

$n = 122.4$

Rounding up:

He must survey 123 adults.

6 0

3 years ago

Margo is creating a pencil caddy in the shape of a triangular prism. She is determining how much wood she needs to build the cad

natka813 [3]

Answer:

a little late

205 1/5 is your answer

Step-by-step explanation:

break down the 3-D figure

Find area of triangle A=1/2bh

=1/2(8 inch)(6 9/10inch)

=1/2(8 inch)(69/10 inch)

=138/5 square inch

then multiply two because you have 2 triangles

=138/5 (2)

= 276/5 square inch

= 55 1/5 sq.in

Find area of rectangle

A = lw

=6 1/4 in (8 in)

= 25/4 (8 in.)

= 50 sq. in.

then multiply by 3 because of the three rectangles

= 50 sq. inch (3)

= 150 sq. in.

Add all together

55 1/5 sq. inch + 150 sq. inch = 205 1/5 sq. inch

4 0

3 years ago

Roberto rowed 20 miles downstream in 2.5 hours. The trip back, however, took him 5 hours. Find the rate that Roberto rows in sti

almond37 [142]

Answer:

Roberto's speed in still water is 6 miles/hour and the river speed is 2 miles/hour

Step-by-step explanation:

Relative Speed

When a body is moving at a constant speed v, the distance traveled in a time t is:

$d=v.t$

When Roberto rows downstream, his speed in still water is added to the speed of the water, making it easier to travel the required distance.

When Roberto rows upstream, his speed in still water is affected by the speed of the water, both are subtracted and the required distance is covered in more time.

Let's call

x = Roberto's rowing speed in still water

y = Speed of the river current

The speed when rowing downstream is x+y, thus the distance traveled is

$d=(x+y).t_1$