According to a study on reptiles from decades ago, the mean lifespan of giant Aldabra tortoises in the wild is  98.3  years. Many of the areas where these tortoises live have become polluted with plastic waste. Because of this, a biologist claims the mean lifespan of these tortoises has decreased. To test this claim, the biologist conducted a study of  21  randomly selected, giant Aldabra tortoises in the wild. In the study, the sample mean lifespan was  96.3  years with a sample standard deviation of  15.2  years. Assume that the population of lifespans of giant Aldabra tortoises in the wild is approximately normally distributed. Complete the parts below to perform a hypothesis test to see if there is enough evidence, at the  0.10  level of significance, to support the claim that  μ , the mean lifespan of giant Aldabra tortoises in the wild, is now less than  98.3  years. (a) State the null hypothesis  H0  and the alternative hypothesis  H1  that you would use for the test. H0 :   H1 :           (b)Perform a  t  test and find the p-value. Here is some information to help you with your  t  test. The value of the test statistic is given by  =t−xμsn . The p-value is the area under the curve to the left of the value of the test statistic.   Student's t Distribution Step 1: Enter the number of degrees of freedom.     Step 2: Select one-tailed or two-tailed.     One-tailed     Two-tailed Step 3: Enter the test statistic. (Round to 3 decimal places.)     Step 4: Shade the area represented by the p-value.       Step 5: Enter the p-value. (Round to 3 decimal places.)     0.1 0.2 0.3 0.4 1 −1 2 −2 3 −3           (c)Based on your answer to part (b), choose what can be concluded, at the  0.10  level of significance, about the claim made by the biologist.       Since the p-value is less than (or equal to) the level of significance, the null hypothesis is rejected. So, there is enough evidence to support the claim that the mean lifespan of giant Aldabra tortoises in the wild is now less than  98.3  years.   Since the p-value is less than (or equal to) the level of significance, the null hypothesis is not rejected. So, there is not enough evidence to support the claim that the mean lifespan of giant Aldabra tortoises in the wild is now less than  98.3  years.   Since the p-value is greater than the level of significance, the null hypothesis is rejected. So, there is enough evidence to support the claim that the mean lifespan of giant Aldabra tortoises in the wild is now less than  98.3  years.   Since the p-value is greater than the level of significance, the null hypothesis is not rejected. So, there is not enough evidence to support the claim that the mean lifespan of giant Aldabra tortoises in the wild is now less than  98.3  years.

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According to a study on reptiles from decades ago, the mean lifespan of giant Aldabra tortoises in the wild is 

98.3

 years. Many of the areas where these tortoises live have become polluted with plastic waste. Because of this, a biologist claims the mean lifespan of these tortoises has decreased. To test this claim, the biologist conducted a study of 

21

 randomly selected, giant Aldabra tortoises in the wild. In the study, the sample mean lifespan was 

96.3

 years with a sample standard deviation of 

15.2

 years. Assume that the population of lifespans of giant Aldabra tortoises in the wild is approximately normally distributed.

Complete the parts below to perform a hypothesis test to see if there is enough evidence, at the 

0.10

 level of significance, to support the claim that 

μ

, the mean lifespan of giant Aldabra tortoises in the wild, is now less than 

98.3

 years.

(a) State the null hypothesis 

H0

 and the alternative hypothesis 

H1

 that you would use for the test.

H0
:
 
H1
:
 
 
 
 

 

(b)Perform a 
t
 test and find the p-value.
Here is some information to help you with your 
t
 test.
  • The value of the test statistic is given by 
    =t−xμsn
    .
  • The p-value is the area under the curve to the left of the value of the test statistic.

 

Student's t Distribution
Step 1: Enter the number of degrees of freedom.
 
 
Step 2: Select one-tailed or two-tailed.
 
 
One-tailed
 
 
Two-tailed
Step 3: Enter the test statistic.
(Round to 3 decimal places.)
 
 
Step 4: Shade the area represented by the p-value.
 
 
 
Step 5: Enter the p-value.
(Round to 3 decimal places.)
 
 
0.1
0.2
0.3
0.4
1
−1
2
−2
3
−3
 
 
 
 

 

(c)Based on your answer to part (b), choose what can be concluded, at the 
0.10
 level of significance, about the claim made by the biologist.

 

 
 
Since the p-value is less than (or equal to) the level of significance, the null hypothesis is rejected. So, there is enough evidence to support the claim that the mean lifespan of giant Aldabra tortoises in the wild is now less than 
98.3
 years.
 
Since the p-value is less than (or equal to) the level of significance, the null hypothesis is not rejected. So, there is not enough evidence to support the claim that the mean lifespan of giant Aldabra tortoises in the wild is now less than 
98.3
 years.
 
Since the p-value is greater than the level of significance, the null hypothesis is rejected. So, there is enough evidence to support the claim that the mean lifespan of giant Aldabra tortoises in the wild is now less than 
98.3
 years.
 
Since the p-value is greater than the level of significance, the null hypothesis is not rejected. So, there is not enough evidence to support the claim that the mean lifespan of giant Aldabra tortoises in the wild is now less than 
98.3
 years.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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