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Serggg [28]
3 years ago
14

Most dermatologists recommend using sunscreens that have a Sun Protection Factor (SPF) of at least 30. One of the authors wanted

to find out whether the SPF of sunscreens used by students at her school exceeds this value on average? To collect data, the author surveyed students in her introductory statistics course and found that in a sample of 52 students the mean SPF was 34.55 and the standard deviation of SPF was 20.12. The data were not strongly skewed.​ Use the Theory-Based Inference applet to find and report the 95% confidence interval for the parameter of interest. Round answers to 4 decimal places, e.g. 0.7523. ​We are 95% confident that the mean SPF level of sunscreen used by all Cal Poly students is between and .
Mathematics
1 answer:
Basile [38]3 years ago
7 0

Answer:  We are 95% confident that the mean SPF level of sunscreen used by all Cal Poly students is between 29.0813 and 40.0187.

Step-by-step explanation:

Given : Significance level : \alpha: 1-0.95=0.05

Sample size : n= 52 , which is a large sample (n>30), so we use z-test.

By using z-value table,

Critical value: z_{\alpha/2}=1.96

Sample mean : \overline{x}= 34.55

Standard deviation : \sigma= 20.12

The confidence interval for population means is given by :-

\overline{x}\pm z_{\alpha/2}\dfrac{\sigma}{\sqrt{n}}

i.e. 34.55\pm(1.96)\dfrac{ 20.12}{\sqrt{52}}

=34.55\pm5.46867829455\\\\\approx34.55\pm5.4687\\\\=(34.55-5.4687, 34.55+5.4687)=(29.0813,\ 40.0187)

Now, the 95% confidence interval for the ppopulation mean = . (29.0813, 40.0187)

Hence, We are 95% confident that the mean SPF level of sunscreen used by all Cal Poly students is between 29.0813 and 40.0187.

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An exterior angle of a triangle is 140 degrees. If the non-adjacent angles are congruent, then what are the measures of all of t
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The measures of all of the interior angles of the triangle are 70 degrees, 70 degrees and 40 degrees

<em><u>Solution:</u></em>

Given that exterior angle of triangle is 140 degrees

The exterior angle of a triangle is equal to the sum of the measures of the two non-adjacent interior angles

Given that adjacent angles are congruent

Let one of the non adjacent interior angles be "x"

x + x = 140

2x = 140

x = 70

So the two interior angles are 70 degrees and 70 degrees

Let us find the third interior angle

The angle sum property of a triangle states that the interior angles of a triangle always add up to 180 degrees

70 + 70 + third angle = 180

third angle = 180 - 70 - 70

third angle = 180 - 140

third angle = 40 degrees

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2 years ago
What two number multiply to -3, but add to -2
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