Answer:
X[bar]= 115
Step-by-step explanation:
Hello!
Every Confidence interval to estimate the population mean are constructed following the structure:
"Estimator" ± margin of error"
Wich means that the intervals are centered around the sample mean. To know the value of the sample mean you have to make the following calculation:
= 115
Since both intervals were calculated with the information of the same sample, you can choose either to calculate the sample mean.
I hope it helps!
Answer:
z=-3.79
Step-by-step explanation:
1) Data given and notation
represent the mean average amount of money on deposit in savings account for the sample
represent the population standard deviation for the sample
sample size
represent the value that we want to test
represent the significance level for the hypothesis test.
z would represent the statistic (variable of interest)
represent the p value for the test (variable of interest)
2) State the null and alternative hypotheses.
We need to conduct a hypothesis in order to check if the mean for the amount of money on deposit in savings account differs from 7500, the system of hypothesis would be:
Null hypothesis:
Alternative hypothesis:
Since we know the population deviation, is better apply a z test to compare the actual mean to the reference value, and the statistic is given by:
(1)
z-test: "Is used to compare group means. Is one of the most common tests and is used to determine if the mean is (higher, less or not equal) to an specified value".
3) Calculate the statistic
We can replace in formula (1) the info given like this:
4)P-value
Since is a two-sided test the p value would be:
5) Conclusion
If we compare the p value and the significance level given we see that
so we can conclude that we have enough evidence to reject the null hypothesis, so we can conclude that the average amount of money deposit in savings account its significantly different from 7500 tons at 1% of signficance.