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3 years ago

7

You measure the lifetime of a random sample of 25 rats that are exposed to 10 Sv of radiation (the equivalent of 1000 REM), for

which the LD 100 is 14 days. The sample mean is = 13.8 days. Suppose that the lifetimes for this level of exposure follow a Normal distribution, with unknown mean μ and standard deviation σ = 0.75 day. What is the 95% confidence interval for μ based on these data?

1 answer:

Slav-nsk [51]3 years ago

4 0

Answer:

CI 95%(μ)= [13.506 ; 14.094]

Step-by-step explanation:

The confidence interval (CI) formula is:

CI (1-alpha) (μ)= mean+- [(Z(alpha/2))* σ/sqrt(n)]

alpha= is the proportion of the distribution tails that are outside the confidence interval. In this case, 5% because 100-90%

Z(5%/2)= is the critical value of the standardized normal distribution. In this case is 1.96

σ= standard deviation. In this case 0.75 day

mean= 13.8 days

n= number of observations . In this case 25

Then, the confidence interval (90%) is:

CI 95%(μ)= 13.8+- [1.96*(0.75/sqrt(25)]

CI 95%(μ)= 13.8+- [1.96*(0.75/5) ]

CI 95%(μ)= 13.8+- (0.294)

CI 95%(μ)= [13.8-0.294 ; 13.8+0.294]

CI 95%(μ)= [13.506 ; 14.094]

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Answer:

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Step-by-step explanation:

If a point (x, y) lies on the terminal side of angle Ф in standard position, then the six trigonometry functions are:

cosФ = $\frac{x}{r}$
sinФ = $\frac{y}{r}$
tanФ = $\frac{y}{x}$
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cotФ = $\frac{x}{y}$

Where r = $\sqrt{x^{2}+y^{2} }$ (the length of the terminal side from the origin to point (x, y)

You should find the quadrant of (x, y) to adjust the sign of each function

∵ Point (1, -8) lies on the terminal side of angle Ф in standard position

∵ x is positive and y is negative

→ That means the point lies on the 4th quadrant

∴ Angle Ф is on the 4th quadrant

∵ In the 4th quadrant cosФ and secФ only have positive values

∴ sinФ, secФ, tanФ, and cotФ have negative values

→ let us find r

∵ r = $\sqrt{x^{2}+y^{2} }$

∵ x = 1 and y = -8

∴ r = $\sqrt{x} \sqrt{(1)^{2}+(-8)^{2}}=\sqrt{1+64}=\sqrt{65}$

→ Use the rules above to find the six trigonometric functions of Ф

∵ cosФ = $\frac{x}{r}$

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∵ sinФ = $\frac{y}{r}$

∴ sinФ = $-\frac{8}{\sqrt{65}}$

∵ tanФ = $\frac{y}{x}$

∴ tanФ = $-\frac{8}{1}$ = -8

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∴ secФ = $\frac{\sqrt{65}}{1}$ = $\sqrt{65}$

∵ cscФ = $\frac{r}{y}$

∴ cscФ = $-\frac{\sqrt{65}}{8}$

∵ cotФ = $\frac{x}{y}$

∴ cotФ = $-\frac{1}{8}$

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