Final answer:
The null hypothesis for a test on the mean lifespan of giant Aldabra tortoises is that it has not decreased and remains at 88.1 years. A one-tailed test is used because the biologist's claim suggests a decrease. Without the actual test statistic and p-value, we cannot determine the conclusion of the hypothesis test.
Step-by-step explanation:
The hypothesis test for the lifespan of giant Aldabra tortoises involves stating the null hypothesis (H0) and the alternative hypothesis (Ha). In this case, the null hypothesis, H0: μ = 88.1, states that the mean lifespan has not decreased and remains at 88.1 years. The alternative hypothesis, Ha: μ < 88.1, claims that the mean lifespan is now less than 88.1 years.
To perform the test, we calculate the test statistic using the given sample mean, standard deviation, and sample size. Since the population standard deviation is not known and the sample size is small (<30), we use the t-distribution:
Select one-tailed test since we are interested in a decrease in lifespan.
Calculate the test statistic (t).
If the calculated p-value is less than the level of significance (α = 0.05), we will reject the null hypothesis indicating there is evidence that the mean lifespan is now less. Without the actual test statistic and p-value provided, we cannot finish the hypothesis test.