Wool Weight Question

Hi, I’m a relatively new knitter (about 1 year) and I just joined the forums!
My question is: In the knitting instructions, when it tells you the wool to use, how do you read this? For example, the pattern I am reading calls for “Blue Sky Alpaca’s Worsted Weight Hand Dyes (4- worsted weight; 50% alpaca/50% wool; each approx 3 1/2 oz/ 100 g and 100 yards/91 m), 5 balls”.
What if I want to use another type of wool? I can use any worsted weight, right? Say I find another wool that is 98 yards/90 m and only 50 grams…Do I go by the weight or the length??? Do I get 10 balls because it’s only 50 grams, or 5 because it’s about the same length?
I think I’m just making myself more confused…help!

it all depends…the way I do it is this…

the TYPE of yarn doesn’t matter too much to me, unless I need it to do what I want the pattern to do (felting for example)

So, I’d find a yarn that matches the guage as closely as possible. You don’t mention that here, but in the pattern , it SHOULD give you a guage, try and find a yarn that will knit up the same guage. (Stitches per inch)

Second the length, I always go by the length, because if the guage is slightly different then you will know for sure you have the right LENGTH of yarn necessary. You might get a ball that is double in length…so you won’t need as many balls as “required” by the pattern.

help some?

The type of yarn - 2, 3, 4 - indicating sport, DK, worsted, is what you’d look for first and these are differentiated by stitch gauge. Then you match the yardage, not the weight of the ball.

Thank you both so much! I hope I don’t seem like too much of a knitting dunce for asking that question!
In case you’re wondering, I am planinng on knitting a gorgeous cable scarf from my newest knitting book [U]Cables Untangles[/U]. This is the wool I am hoping to use: http://www.ramwools.com/index.cfm?pageID=3&section=143&prodID=3868 in “Anemone”.