Answer: 
Step-by-step explanation:
Given : Sample size : n= 9
Degree of freedom = df =n-1 =8
Sample mean : 
sample standard deviation : 
Significance level ; 
Since population standard deviation is not given , so we use t- test.
Using t-distribution table , we have
Critical value = 
Confidence interval for the population mean :

90% confidence interval for the mean value will be :






Hence, the 90% confidence interval for the mean value= 
Three students want to estimate the mean backpack weight of their schoolmates. To do this, they each randomly chose 8 schoolmates and weighed their backpacks. Then as per the given sample data,
(a) The sample means of the backpacks are: 6.375,6.375,6.625
(b) Range of sample means: 0.25
(c)The true statement is: The closer the range of the sample means is to 0, the less confident they can be in their estimate.
For the first sample, mean= 6.375
For the second sample, mean= 6.375
For the third sample, mean= 6.625
Range of sample means=Maximum Mean- Minimum Mean
= 6.625 - 6.375
= 0.25
The students will estimate the average backpack weight of their classmates using sample means, the true statement is:
The closer the range of the sample means is to 0, the more confident they can be in their estimate.
Learn more about range here:
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Answer:
1. x = 36 equation is x + 2x + 9 = 117, then solve for x
2. x = 50 equation is x + x + 12 = 112, then solve for x
Step-by-step explanation: