Calculating Mean & SD for Number of Cars per Household

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The discussion revolves around calculating the mean and standard deviation for the number of cars per household based on a frequency distribution from a sample of 530 households. The initial calculations provided by a user were incorrect, with a mean of 106 and a standard deviation of 48.13, which were deemed unrealistic. Participants emphasized the need to correctly interpret the frequency distribution to find the mean and standard deviation, suggesting a mean of 3 and a standard deviation of approximately 1.58. The importance of understanding weighted means for categorical data was highlighted as a crucial step in solving the problem accurately. Ultimately, the user acknowledged their misunderstanding and indicated they had resolved the issue.
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A random sample of 530 households resulted in the following frequency distribution for a number of cars per household. Find the mean and standard deviation.
Number of cars ¦ Frequency
1 ¦ 61
2 ¦ 108
3 ¦ 179
4 ¦ 118
5 ¦ 64
Sorry don't know how to put this in a box. Under cars it's 1,2,3,4,5. Under frequency it'a 61,108,179,118,64. I typed the Freq. into my calculator and my mean was 106 and my standard deviation was 48.13.
I was marked off 6 points. Shoud I have just done cars? Put that into my calculator and my mean would be 3 and my sd be 1.6?
Thanks
 
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Try re-reading the problem then try to understand the question. It's asking you to find the mean number of cars, right? Your answer was 106. Does that make sense? Do you really think the mean number of cars per household is 106? I wish I had that many cars...
 
The mean would be 3 and the sd be 1.6 ? Thanks
 
If you're rounding, 3 is the mean. On the other hand, 1.6 seems a bit off.
 
Sd comes out to 1.58.
 
You should post the steps you are taking to solve the problem. That way we can see where you are making an error and correct it.
 
Oh god, I just realized how you're coming up with mean = 3 and stdev = 1.6...

Re-read the question, and again try to understand the question. After you've done that, answer this: what is the total number of cars?
 
rowdy3 said:
A random sample of 530 households resulted in the following frequency distribution for a number of cars per household. Find the mean and standard deviation.
Number of cars ¦ Frequency
1 ¦ 61
2 ¦ 108
3 ¦ 179
4 ¦ 118
5 ¦ 64
Sorry don't know how to put this in a box. Under cars it's 1,2,3,4,5. Under frequency it'a 61,108,179,118,64. I typed the Freq. into my calculator and my mean was 106 and my standard deviation was 48.13.
I was marked off 6 points. Shoud I have just done cars? Put that into my calculator and my mean would be 3 and my sd be 1.6?
Thanks

Hint: Look up weighted means (of an ordered categorical variable). That's all I'm going to say. If you come back, someone else may help you.
 
Thanks I got it now.
 

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