Anyone want to help with my statistics homework?

[flowlikeocean]

Hi, I've been sitting in my room for about an hour, staring at one question from my statistics homework. Even though my teacher isn't grading it I still want to understand it, and something about the problem just doesn't make sense for me. (I'm sure once I have it started, I'll feel like an idiot for not being able to do it in a few minutes, but as of now I'm lost)

So, I'm reaching out to you, TalkBass OT, the problem is as follows:

A study claims that the distribution of the life expectancy of a single celled organism is moderately left skewed with a mean of 45.5 days and a standard deviation of 3.4 days. Find the probability that an organism selected at random will live for 49 or more days. Verify the necessary conditions and justify any assumptions made.

So far, I've stated that the selection of an organism is independent (10n</= N (we can assume there are more than ten in the population)), and that from there I'm lost.

Really, I would just like some help starting the problem, after that I can do the rest (hopefully ).

Thanks for the time, and rock on when academics permit,
Ben

[fdeck]

I suggest looking up the graphs for some of the familiar distributions, choosing one that seems to satisfy the problem set-up, and use that distribution to solve the problem. If nothing else, it will allow you to practice working through the problem for a known distribution.

By the way, what else do you know about the distribution, that's implied by being the lifetime of a cell?

[flowlikeocean]

Nothing else is stated, the distribution isn't normal, and no quantitative value is assigned to "slightly left skewed." Also, since the SRS isn't "large," the central limit theory can't be used.

[CapnSev]

What chapter are you on? Are you doing t-tests, chi squares?

[UncleFluffy]

Originally Posted by flowlikeocean

A study claims

Do you have a value for the probability that the claim accurately reflects reality?

[flowlikeocean]

Originally Posted by CapnSev

What chapter are you on? Are you doing t-tests, chi squares?

This is from sampling distribution work. Sorry if that isn't descriptive enough.

Originally Posted by UncleFluffy

Do you have a value for the probability that the claim accurately reflects reality?

No. I believe that the question leads you to assume that the stipulated figures (mean 45.5 standard dev. 3.4 days) are parameters, however the " Slightly Left Skewed " is confusing me, as I have no quantitative value for "Slightly left."

[fdeck]

Originally Posted by flowlikeocean

Nothing else is stated, the distribution isn't normal, and no quantitative value is assigned to "slightly left skewed." Also, since the SRS isn't "large," the central limit theory can't be used.

Do you know anything about the upper and lower bounds on a lifetime?

[flowlikeocean]

Originally Posted by fdeck

Do you know anything about the upper and lower bounds on a lifetime?

Unfortunately, no, all the information I have is in the OP.

[UncleFluffy]

I just did what I automatically do and Google any undefined terms. This thread is #8 on the results for "moderately left skewed".

Them google guys are FAST.

[flowlikeocean]

Haha, well shows how important TBOT is, we're #8! (#1 in everyone's heart)

[The Last Rebel]

I really wish I could help you, but in my stats class we play dice games. My teacher would probably think that question is in a foreign language if he saw it.

[flowlikeocean]

Well, I wish I was in your stats class :bawls:. Anyway, I think I'll just ask a classmate tomorrow morning, thanks for the support, though, OT!

[fdeck]

Originally Posted by flowlikeocean

Unfortunately, no, all the information I have is in the OP.

Do any of the cells have a negative lifetime?

[flowlikeocean]

I would guess not, as negative lifetime is impossible, life is all real numbers above 0.