Question: Calculating P-Values From Z-Scores

7

7

Manu Prestat ♦

**3.8k**wrote:your expression is good. Just don't forget, if relevant, to take into account the two-sided characteristic of the test, it would be then:

```
pvalue2sided=2*pnorm(-abs(z))
```

And, if you think you need to use the "apply" function, you might need to think about multitesting correction... but, I agree, this is another topic ;-)

1

Thanks! my test is one-sided as I am looking at enrichment only

1

Gjain ♦

**5.1k**wrote:Hi Diana,

I was explaining the same thing to my friend this morning.

here is a very nice and useful link: Calculating p Values

- Calculating a Single p Value From a Normal Distribution
- Calculating a Single p Value From a t Distribution
- Calculating Many p Values From a t Distribution

I hope this helps.

0

Emre •

**70**wrote:Based on the previous answers and comments, here is a function that considers both the one-sided case (two alternatives, observed scores are greater / z is positive: "+", observed scores are lower / z is negative: "-") and two sided case ("NULL").

convert.z.score<-function(z, one.sided=NULL) { if(is.null(one.sided)) { pval = pnorm(-abs(z)); pval = 2 * pval } else if(one.sided=="-") { pval = pnorm(z); } else { pval = pnorm(-z); } return(pval); }

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