Answer:

Step-by-step explanation:
The firm tests 75 parts, and finds that 0.25 of them are notusable
n = 75
x = 0.25 \times 75 = 18.75≈19



Confidence level = 95%
So, Z_\alpha at 95% = 1.96
Formula of confidence interval of one sample proportion:


Confidence interval 
Answer: I think it’s b which is also 5
Step-by-step explanation:
In the link
if I did it wrong someone pls correct me
There is : 3 pencils
4 Bubble gums
2 sports cards
In each favor bag
Concave up is U-shaped.
There will be a inflection/critical point f'(x) =0 then a negative slope f'(x) = neg then another inflection/critical point f'(x) =0 at the bottom of the U-shape then a positive slope to last inflection/critical point. The interval for the Concave Up shape is the first and last inflection points.