solo diving survey results

[skip]

Many of you took the solo diving survey on "surveymonkey" at my request posted here on the forum awhile back. Preliminary results are in with responses from 298 divers (cave, wreck, reef, rec and tec). All numbers are 1-10 with 10 being most safe and 1 being least safe.

Is scuba diving safe? Mean is 8.02 with sd of 1.65.
Is buddy diving safe? Mean is 7.66 with sd of 1.79
Is group diving safe? Mean is 6.82 with sd of 2.10
Is solo diving safe? Mean is 7.00 with sd of 2.2
Can solo training make it safe? Mean is 7.83 with sd of 2.95

with such a large n, statistically significant results are a bit easy to find. even small differences become "significant." But here goes:

buddy diving considered safer than solo diving (7.66 vs 7.00).
buddy diving is safer than group diving (7.66 vs 6.82).
solo diving with training can be as safe as buddy diving and safer than group diving, and safer than solo diving without training (7.83 vs 7.66 and 6.82 and 7.00).

these differences are pretty small so I would not argue if someone held that personal opinions on safety all come out pretty much the same whether we are considering diving with or without a buddy or group.

I will be breaking it down by type of diver and gender, maybe age too...and report back then.

Thanks to all who took the time to help out.

-skip

[Luxrok]

I am assuming sd mean Standard Deviation. If so, I couldn't remember what it meant so I looked it up on Wikipedia. Here is what I found:

In probability and statistics, the standard deviation is a measure of the dispersion of a collection of values. It can apply to a probability distribution, a random variable, a population or a data set. The standard deviation is usually denoted with the letter σ (lowercase sigma). It is defined as the root-mean-square (RMS) deviation of the values from their mean, or as the square root of the variance. Formulated by Galton in the late 1860s,[1] the standard deviation remains the most common measure of statistical dispersion, measuring how widely spread the values in a data set are. If many data points are close to the mean, then the standard deviation is small; if many data points are far from the mean, then the standard deviation is large. If all data values are equal, then the standard deviation is zero. A useful property of standard deviation is that, unlike variance, it is expressed in the same units as the data.

So the quick translation for me is that most of the responses came within the sd on either side of the mean. Correct me if I am wrong.

You can find that definition for Standard Deviation on Wikipedia.

No onto my question, what do you mean by such a large N?

Hope that is as helpful to you as it is me.
Hans

[scblade27]

N is normally what is used for the sample size. In this case it is the 298 divers that responded. The bigger the N/people that respond, the more significant the results. The more significant the results, the more you can generalize about the total population.

i.e. If you asked 10 Americans who they were voting for president, your results would not be very significant. If you asked 200 million Americans, you would have much more reliable data.

[Luxrok]

N is normally what is used for the sample size. In this case it is the 298 divers that responded. The bigger the N/people that respond, the more significant the results. The more significant the results, the more you can generalize about the total population.

i.e. If you asked 10 Americans who they were voting for president, your results would not be very significant. If you asked 200 million Americans, you would have much more reliable data.

Thanks for the explanation. I hope I wasn't the only fool wondering.

[akcaver]

Within 1 standard deviation of the mean value, you should have 95% of all the answers. That means in the first question, Is Scuba Diving Safe? 95% of all the answers were between 6.37 and 9.67, and 98% of all the answers were between 4.72 and 11.32 (or 10, but in general stats 98% of all values/answers come within 2 standard deviations of the mean). Hope that helps also.

[MORGAN]

I still have bad memories of my statistics and probability courses after many years. I was forced to take them - I was a wildlife biology major; I wanted to be in the woods counting deer turds!

I still have a question about this standard deviation thing: How can anything that's standard be considered a deviation? Ain't that one o' them oxygenmaroons?

Mike

PS - I enjoy your research projects, Skip. I'm eagerly anticipating your study on the personality disord- I mean characteristics of cave divers. The analyses you sent Tracy and I were almost embarrassingly accurate.