Answer:
The null hypothesis is given as
while the alternate hypothesis is 
Step-by-step explanation:
As per the the given data
p1=Proportion of Homeowners who would buy the security system
p2=Proportion of Renters who would buy the security system
As the null hypothesis states that there is no difference in the test thus it is given as

This states that there is no difference between the probabilities of the homeowners buying the security system and the renters buying the security system.
The Alternative hypothesis is the other possibility of the null hypothesis. i.e It negates the null Hypothesis and is given as

The average mean is equal to the sum of numbers divided by the total numbers, which means that the mean of 230 with 80 numbers gives that the sum is 230*80 = 18400, if you apply the formula described in the beginning. Since 4 numbers are known and are<span> 145,156,210, and 255, their sum is </span>766. The sum of the list is equal to the sum of the numbers without the sum of 4 known numbers, so it's equal to 18400 - 766 = 17634, from which we can see that the Mean = (Sum Of List)/(80 - 4)
= 17634/76
= 232.02