Fat Caliper Accurate

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It seems like I play with the same lb over and over again through out the week.... then one day I will finally see a new lower weight on the scale by over a lb. My measurements are the same thing. If I look at a larger period of time I have definatly made improvemnts. But when I look in the mirror I can tell that my body is making dramtic progress. I know I should be happy with it.... But I wonder if its my own perception. I have also noticed that my fat is changing. It used to be hard in my abdominal area, but now its really soft and is just kind of flabby. I am wondering if using a fat caliper to measure body fat is accurate? According to my numbers in the last week I have lost 2.5 lbs, 1" around my waist and 6 lb of fat (I used the measurment method for the first number since I didnt have a fat caliper last week) Can that be accurate? I am eating right and doing P90X by the book 6 days a week.