A sample of 1714 cultures from individuals in Florida diagnosed with a strep infection was tested for resistance to the antibiotic penicillin; 973 showed partial or complete resistance to the antibiotic.(a) Describe the population and explain in words what the parameter p is.(b) Give the numerical value of the statistics that estimates p.(c) Give a 95% confidence interval for the proportion of step cultures from Florida patients showing partial or complete resistance to penicillin. What can we conclude?

Respuesta :

Answer:

a) [tex]p[/tex] represent the real population proportion of people who showed partial or complete resistance to the antibiotic

b) [tex]\hat p=\frac{973}{1714}=0.568[/tex] represent the estimated proportion of people who showed partial or complete resistance to the antibiotic

c) We are confident (95%) that the true proportion of individuals in Florida diagnosed with a strep infection was tested for resistance to the antibiotic penicillin present partial or complete resistance to the antibiotic is between 54.5% to 59.1%.  

Step-by-step explanation:

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

The margin of error is the range of values below and above the sample statistic in a confidence interval.

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

Part a

Description in words of the parameter p

[tex]p[/tex] represent the real population proportion of people who showed partial or complete resistance to the antibiotic

[tex]\hat p[/tex] represent the estimated proportion of people who showed partial or complete resistance to the antibiotic

n=1714 is the sample size required

[tex]z_{\alpha/2}[/tex] represent the critical value for the margin of error

The population proportion have the following distribution  

[tex]p \sim N(p,\sqrt{\frac{p(1-p)}{n}})[/tex]

Part b

Numerical estimate for p

In order to estimate a proportion we use this formula:

[tex]\hat p =\frac{X}{n}[/tex] where X represent the number of people with a characteristic and n the total sample size selected.

[tex]\hat p=\frac{973}{1714}=0.568[/tex] represent the estimated proportion of people who showed partial or complete resistance to the antibiotic

Part c

The confidence interval for a proportion is given by this formula

[tex]\hat p \pm z_{\alpha/2} \sqrt{\frac{\hat p(1-\hat p)}{n}}[/tex]

For the 95% confidence interval the value of [tex]\alpha=1-0.95=0.05[/tex] and [tex]\alpha/2=0.025[/tex], with that value we can find the quantile required for the interval in the normal standard distribution.

[tex]z_{\alpha/2}=1.96[/tex]

And replacing into the confidence interval formula we got:

[tex]0.568 - 1.96 \sqrt{\frac{0.568(1-0.568)}{1714}}=0.545[/tex]

[tex]0.568 + 1.96 \sqrt{\frac{0.56(1-0.56)}{1714}}=0.591[/tex]

And the 95% confidence interval would be given (0.545;0.591).

We are confident that about 54.5% to 59.1% of individuals in Florida diagnosed with a strep infection was tested for resistance to the antibiotic penicillin present partial or complete resistance to the antibiotic.  

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