BookmarkSubscribeRSS Feed
Pepperoni
Calcite | Level 5


Hello everyone,

I have multiple groups - each one different from the others. All groups are exposed to one chemical. For each group, I have derived a number that denotes the number of milligrams per liter of the chemical that takes to be toxic to that group. The number has a 95% confidence interval, and is the aggregate of multiple testing replicates.

Group A is the "standard" - the wild type. The other groups have been altered genetically in specific ways (to see whether a given gene is involved in the toxicity).

Here are sample numbers (95% CI in parentheses):

Group A = 13,607 (10,302 - 20,338)

Group B = 12,222 (8,251 - 27,120)

Group C = 16,912 (11,232 - 28,327)

How can I run a procedure that will tell me whether Group B is statistically different from Group A? That Group C is statistically different from Group A?

I guess I mean one-way ANOVA. Could you suggest what code I would run? I am using SAS 9.3.

Many thanks!

"Peppy"

6 REPLIES 6
Reeza
Super User

Do you have the raw data available, ie each result from the replicate? It's more accurate to perform analysis on that data.

In general, if your confidence intervals overlap then the results are not statistically different.

SteveDenham
Jade | Level 19

And given that these strongly overlap, I would suspect that they are not different.  However, without some knowledge of how the CI's were constructed, I don't want to venture too far out on this one.

Steve Denham

Ksharp
Super User

proc glm + lsmeans  for multi-comparison ?

SteveDenham
Jade | Level 19

If you have the raw numbers, that should work, if there are no real complicating factors.

However, I suspect there is a lot more behind the scene here--I think there is some inverse regression.  I also wonder how a toxic dose is defined--lethal to all in the group, LD50 (by probit regression), NOEL by lowest level tested, etc.  The toxicology world has a lot of stuff going on, and without knowing which method was used, I worry that without taking this into account, we get something unexpected.

Still, those confidence bounds are huge in comparison to the mean, and are not symmetric around the mean, so I think there is more here than meets the eye.

Steve Denham

Ksharp
Super User

WOW. Too many things I don't know .Steve .

Pepperoni
Calcite | Level 5

Thank you all so much! You have been so helpful and kind!!

sas-innovate-2024.png

Don't miss out on SAS Innovate - Register now for the FREE Livestream!

Can't make it to Vegas? No problem! Watch our general sessions LIVE or on-demand starting April 17th. Hear from SAS execs, best-selling author Adam Grant, Hot Ones host Sean Evans, top tech journalist Kara Swisher, AI expert Cassie Kozyrkov, and the mind-blowing dance crew iLuminate! Plus, get access to over 20 breakout sessions.

 

Register now!

What is ANOVA?

ANOVA, or Analysis Of Variance, is used to compare the averages or means of two or more populations to better understand how they differ. Watch this tutorial for more.

Find more tutorials on the SAS Users YouTube channel.

Discussion stats
  • 6 replies
  • 1633 views
  • 0 likes
  • 4 in conversation