Confused on Ribbing Stitch Instructions
 

I am starting on a sweater pattern - however, my knowledge of knitting is VERY LOW. The guage says to cast on 25 stitches and then to complete 28 rows with P 3, K 1 ribbing.

I am confused because the stitches ate a multiple of 4 plus 1 and
I also don't know if this means every row should be P 3, K 1 or if I should alternate between that and K 3, P 1. A site mentions a slip stitch, but does that mean slip as if to knit or as if to purl.

Any help most appreciated! Happy Holidays!!

Just to be clear, it says for the gauge swatch you should cast on 25 sts?
The ribbing pattern would be: row 1: p3, k1; row 2 knit the knits and purl the purls (as they appear on this side).
Do the instructions tell you to slip a stitch?
Can you link to your pattern, that is generally quite helpful.

Always include the pattern name and a link if its possible. Every pattern is a little different and there are probably thousands of them.

You need to use more stitches for a swatch anyway. Since the stitch repeat is 4 sts, CO 32 stitches, then measure across 25 sts without including the edge stitches. When you slip the first stitch, it's slipped purlwise, but isn't always necessary on the edges.

Yes, more stitches in the swatch allows you to measure over the center 25sts and gives you a more accurate measure of gauge.
Your second suggestion is right. You'll be alternating between p3k1 and k3p1 rows to give the rib pattern. Or as GG suggests, knit the Vs and purl the bumps and you'll have ribbing.

Just to be clear, you'll reverse the pattern of knits and purls on the alternate rows if you're knitting the piece flat (not in the round). I assume you are, but that's an important distinction to make.

As I understand it, when you slip a stitch it's always slipped as if to purl unless it's part of a decrease or the pattern specifically says to slip it as if to knit. There may (probably ARE) exceptions to the exceptions to the rule too. I'm not aware of any purlwise decreases that involve slipped stitches, but there are a LOT of things I'm unaware of. There are far more experienced folks here to answer that question. But chances are that if you encounter something like that in a pattern, it will be sufficiently unusual that the pattern writer will give instructions on it.

Thanks for the Help
 

This pattern comes from Simply Beautiful Knitting, a 2-ring binder. Though the book is mentioned on several sites, I can't find a link to the pattern. Under Guage, it just says

25 sts and 28 rows to 4" on No. 6 needles over p 3, k 1 ribbing

Appreciate your advice on the need to alternate - maybe I am making too much of the extra stitch

Yes, the 'extra stitch' probably won't be there for the cast on. It just so happens that the 4" gauge for this pattern was achieved over 25 sts, rather than 24 or 26, or 22. A gauge swatch should always be done with several more sts than given for 4" in order to be more accurate.

Thanks very much - I will try and tackle the pattern - I'm sure you'll be hearing from me given my lack of know=how in this area. Appreciate the advice.

You'll know right away that you've got it when you see the rib pattern. You'll want the knit stitch to stack up over the other knit stitch and the purl sts to stack up in a column over the other purls.