terminator
New member
- Joined
- Jan 26, 2012
- Messages
- 4
A survey of 1600 randomly selected people in France showed that 74% have cellphones.
a)Determine the mean the sd.
Mean = 1184
SD = 17.55
b) Determine the 90% confidence interval for the people who have cellphones.
I know that the confidence interval should be for 95% for a normal distribution. ("For a data that have a normal distribution the confidence interval is mean +/-1.96 SD. This is the range of values that lie within 1.96 SD from mean.)
Should I calculate a different coefficient for 90% (if 95% is 1.96 then for 90% is 1.8556842) or is the question wrong and was supposed to ask for 95% interval?
If I use this(1.86) coefficient I get that the number of people is between 1151 and 1216
if I use 1.96 I get 1218 and 1150
Please help
a)Determine the mean the sd.
Mean = 1184
SD = 17.55
b) Determine the 90% confidence interval for the people who have cellphones.
I know that the confidence interval should be for 95% for a normal distribution. ("For a data that have a normal distribution the confidence interval is mean +/-1.96 SD. This is the range of values that lie within 1.96 SD from mean.)
Should I calculate a different coefficient for 90% (if 95% is 1.96 then for 90% is 1.8556842) or is the question wrong and was supposed to ask for 95% interval?
If I use this(1.86) coefficient I get that the number of people is between 1151 and 1216
if I use 1.96 I get 1218 and 1150
Please help