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matrenka [14]
3 years ago
5

A cat-lover claims that cats are just as smart as dogs. In order to back this claim up with some evidence she organizes a study

at a large local pet daycare center. A random sample of 40 cats are selected and a random sample of 40 dogs are selected. Each of the selected animals is given one hour with a trainer in which the trainer attempts to teach them to roll over. Upon conclusion of the training, the proportion of dogs and proportion of cats that have learned this skill is computed. The trainer reports that she is 90% confident that the true difference in the proportion of all dogs and all cats (pD – pC) that can learn this skill with one hour of training is between ­–0.05 to 0.28.
Which of the following conclusions can be made based upon this confidence interval?

(A) Because most of the values in the confidence interval are positive, this proves that dogs are smarter than cats
(B) Because the point estimate of the confidence interval is positive, there is convincing evidence that the proportion of all dogs that can learn the skill with one hour of training is greater than the proportion of all cats that can learn the skill with one hour of training.
(C) Because O is contained in the interval, there is not convincing evidence that the proportion of all dogs that can learn the skill with one hour of training differs from the proportion of all cats that can learn the skill with one hour of training.
(D) Because 0.115 is contained in the interval, there is not convincing evidence of a difference in the population proportions.
(E) Because the margin of error of the confidence interval is greater than 0.05, there is not convincing evidence that the proportion of all dogs that can learn the skill with one hour of training differs from the proportion of all cats that can learn the skill with one hour of training.
Mathematics
1 answer:
Veronika [31]3 years ago
7 0

Answer:

(C) Because 0 is contained in the interval, there is not convincing evidence that the proportion of all dogs that can learn the skill with one hour of training differs from the proportion of all cats that can learn the skill with one hour of training.

Step-by-step explanation:

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Ind the area of the rectangle, in square centimeters. Rectangle ABCD Length = 20 cm Width = 9 cm​
alexdok [17]

Answer:

180 cm^3

Step-by-step explanation:

A=lw

A=20×9

A=180

4 0
3 years ago
Dual-energy X-ray absorptiometry (DXA) is a technique for measuring bone health. One of the most common measures is total body b
sesenic [268]

Answer:

\bar d=\frac{\sum_{i=1}^n d_i}{n}=-0.001

s=\sqrt{\frac{\sum_{i=1}^n (x_i -\bar X)^2}{n-1}}=0.0095

-The sample is too small to make judgments about skewness or symmetry.

H0:\mu_{1}=\mu_{2}

H1:\mu_{1} \neq \mu_{2}

t=\frac{1.173-1.174}{\sqrt{\frac{0.1506^2}{8}+\frac{0.1495^2}{8}}}=-0.013

p_v =2*P(t_{(14)}

So the p value is a very high value and using any significance level for example \alpha=0.05, 0,1,0.15 always p_v>\alpha so we can conclude that we have enough evidence to FAIL to reject the null hypothesis, and a we don't have a significant difference between the two means.

Step-by-step explanation:

First we need to find the difference defined as:

(Operator 1 minus Operator 2)

d1=1.326-1.323=0.003      d2=1.337-1.322=0.015

d3=1.079-1.073=0.006     d4=1.229-1.233=-0.004

d5=0.936-0.934=0.002   d6=1.009-1.019=-0.01

d7=1.179-1.184=-0.005      d8=1.289-1.304=-0.015

Now we can calculate the mean of differences given by:

\bar d=\frac{\sum_{i=1}^n d_i}{n}=-0.001

And for the sample deviation we can use the following formula:

s=\sqrt{\frac{\sum_{i=1}^n (x_i -\bar X)^2}{n-1}}=0.0095

Describe the distribution of these differences using words. (which one is correct)

We can plot the distribution of the differences with the folowing code in R

differences<-c(0.003,0.015,0.006,-0.004,0.002,-0.01,-0.005,-0.015)

hist(differences)

And we got the image attached. And we can see that the distribution is right skewed but we don't have anough info to provide a conclusion with just 8 differnences.

-The sample is too small to make judgments about skewness or symmetry.

Use a significance test to examine the null hypothesis that the two operators have the same mean. Give the test statistic. (Round your answer to three decimal places.)

\bar X_{1}=1.173 represent the mean for the operator 1

\bar X_{2}=1.174 represent the mean for the operator 2

s_{1}=0.1506 represent the sample standard deviation for the operator 1

s_{2}=0.1495 represent the sample standard deviation for the operator 2

n_{1}=8 sample size for the operator 1

n_{2}=8 sample size for the operator 2

t would represent the statistic (variable of interest)

Concepts and formulas to use

We need to conduct a hypothesis in order to check if the means for the two groups are the same, the system of hypothesis would be:

H0:\mu_{1}=\mu_{2}

H1:\mu_{1} \neq \mu_{2}

If we analyze the size for the samples both are less than 30 so for this case is better apply a t test to compare means, and the statistic is given by:

t=\frac{\bar X_{1}-\bar X_{2}}{\sqrt{\frac{s^2_{1}}{n_{1}}+\frac{s^2_{2}}{n_{2}}}} (1)

t-test: Is used to compare group means. Is one of the most common tests and is used to determine whether the means of two groups are equal to each other.

Calculate the statistic

We can replace in formula (1) like this:

t=\frac{1.173-1.174}{\sqrt{\frac{0.1506^2}{8}+\frac{0.1495^2}{8}}}=-0.013

Statistical decision

For this case we don't have a significance level provided \alpha, but we can calculate the p value for this test. The first step is calculate the degrees of freedom, on this case:

df=n_{1}+n_{2}-2=8+8-2=14

Since is a bilateral test the p value would be:

p_v =2*P(t_{(14)}

So the p value is a very high value and using any significance level for example \alpha=0.05, 0,1,0.15 always p_v>\alpha so we can conclude that we have enough evidence to FAIL to reject the null hypothesis, and a we don't have a significant difference between the two means.

8 0
3 years ago
PLEASE HELP <br> GIVEN THE GRAPH OF A FUNCTION, IDENTIFY ALL ITS FEATURES
Novosadov [1.4K]

Answer:

Once again, it’s a nonlinear function.

Graph is not in a straight line.

It has arrows on it’s ends.

Step-by-step explanation:

This line is squiggly. It is bent at the origin and some others. It also has arrows at the line’s ends.

8 0
2 years ago
Is 1/3 a irrational number?
LenKa [72]

Answer: 13 is a rational number

Step-by-step explanation: By definition, a rational number is a number q that can be written as a fraction in the form q=a/b where a and b are integers and b≠0. So, 1/3 is rational because it is exactly what you get when you divide one integer by another.

8 0
2 years ago
What is the measure of cº?<br> A. 7.5°<br> B. 15<br> C. 30°<br> D. 45
mylen [45]

Answer:

x = 15

Step-by-step explanation:

The sum of the angles in a triangle is 180º

3x + 5x + 4x = 180

Combine like terms

12x = 180

Divide both sides by 12

x = 15

C = 5x

C = 5 * 15

C = 75º

6 0
3 years ago
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