Can you please tel, me what is step 3

Customers arrive at a movie theater at the advertised movie time only to find that they have to sit through several previews and

sergij07 [2.7K]

Answer:

a) sample size is 40

Step-by-step explanation:

(a)

$\sigma=4$ minutes

Margin of error, E is 75 seconds E=75/60= 1.25 minutes.

The level of significance $\alpha= 0.05$ for 95% level of significance

For 95% confidence interval $z_{\frac{\alpha}{2}}=1.96$ from standard deviation table

Sample size required, n

$n=\left (\frac{z_{\frac{\alpha}{2}}\cdot \sigma}{E} \right )^{2}=\left (\frac{1.96\cdot4}{75/60} \right )^{2}=39.337984$

Rounding off, n=40

Sample size =40

Keywords:

95% confidence, sample size, Wall Street Journal

3 0

4 years ago

Sandra exerci 2/3 hours every day for two weeks while she was on vacation how many hours did Sandra exercise during her vacation

vagabundo [1.1K]

I think the us 1 1/3. 2/3 x 2/1=4/3=1 1/3. Hope it helps and I hope it right.

3 0

3 years ago

A torus is formed by rotating a circle of radius r about a line in the plane of the circle that is a distance R (> r) from th

jeyben [28]

Consider a circle with radius $r$ centered at some point $(R+r,0)$ on the $x$ -axis. This circle has equation

$(x-(R+r))^2+y^2=r^2$

Revolve the region bounded by this circle across the $y$ -axis to get a torus. Using the shell method, the volume of the resulting torus is

$\displaystyle2\pi\int_R^{R+2r}2xy\,\mathrm dx$

where $2y=\sqrt{r^2-(x-(R+r))^2}-(-\sqrt{r^2-(x-(R+r))^2})=2\sqrt{r^2-(x-(R+r))^2}$ .

So the volume is

$\displaystyle4\pi\int_R^{R+2r}x\sqrt{r^2-(x-(R+r))^2}\,\mathrm dx$

Substitute

$x-(R+r)=r\sin t\implies\mathrm dx=r\cos t\,\mathrm dt$

and the integral becomes

$\displaystyle4\pi r^2\int_{-\pi/2}^{\pi/2}(R+r+r\sin t)\cos^2t\,\mathrm dt$

Notice that $\sin t\cos^2t$ is an odd function, so the integral over $\left[-\frac\pi2,\frac\pi2\right]$ is 0. This leaves us with

$\displaystyle4\pi r^2(R+r)\int_{-\pi/2}^{\pi/2}\cos^2t\,\mathrm dt$

Write

$\cos^2t=\dfrac{1+\cos(2t)}2$

so the volume is

$\displaystyle2\pi r^2(R+r)\int_{-\pi/2}^{\pi/2}(1+\cos(2t))\,\mathrm dt=\boxed{2\pi^2r^2(R+r)}$

6 0

3 years ago

The votes for president in a club election were: Smith: 24 Munoz: 32 Park: 20 Find the following ratios and write in simplest fo

Setler79 [48]

Answer:

Step-by-step explanation:

Smith=24

Munoz=32

Park=20

Total votes=24+32+20=76

Ratio of votes for Munoz to Smith

32:24

=4:3

Ratio of votes for Park to Munoz

20:32

=5:8

Ratio of votes for Smith to total votes

24:76

=6:19

Ratio of votes for Smith to Munoz to Park

24:32:20

=6:8:5

4 0

4 years ago

If the vertex of a parabola is at the point (-2, 5), then the equation for the axis of symmetry for the parabola is x = -2. True

balandron [24]

Answer:

true

Step-by-step explanation:

thats really it i believe its true

6 0

2 years ago