Answer:
a: 28 < µ < 34
Step-by-step explanation:
We need the mean, var, and standard deviation for the data set. See first attached photo for calculations for these...
We get a mean of 222/7 = 31.7143
and a sample standard deviation of: 4.3079
We can now construct our confidence interval. See the second attached photo for the construction steps.
They want a 90% confidence interval. Our sample size is 7, so since n < 30, we will use a t-score. Look up the value under the 10% area in 2 tails column, and degree of freedom is 6 (degree of freedom is always 1 less than sample size for confidence intervals when n < 30)
The t-value is: 1.943
We rounded down to the nearest person in the interval because we don't want to over estimate. It said 28.55, so more than 28 but not quite 29, so if we use 29 as the lower limit, we could over estimate. It's better to use 28 and underestimate a little when considering customer flow.
For the first part:Every shirt she grabs, will cost her dollars, so if she grabs 3 shirts, then the cost of the shirts is:
With the same rationale, if she grabs 2 pairs of jeans, the cost of the jeans is:
So, her total is:
If you subtract 3 from the total, then the expression is:
For the second part:If she's paying 3 less for each shirt, then the cost of 3 shirts will become:
In the same fashion, for the two jeans:
So the expression for the total cost is:
For number three:The amounts are different because the cost of the total purchase is different than the cost of each element that makes up the total purchase.
For number four:If you're the owner, you want to give the smallest amount of discount (the one in part 1/a).
So you could clarify by saying there's 3 dollars of the TOTAL purchase's cost.
The first thing we must do for this case is to define variables.
We have then:
x = Tim's age
Now we write the equation:
x + 7 = 3 (x-19)
Answer:
Tim's age in 7 years will be three times what it was 19 years ago:
x + 7 = 3 (x-19)
Here is all the work with it
