VA hospital rates are “riskadjusted.” That is, they take into account how sick patients were before they were admitted to the hospital.
VA hospitals are shown to be “Lower” or “Higher Than VA National Rate” only if we can be 95% certain that the difference between the hospital’s rates and the VA National rate is not due to chance. All others are shown in the “Within the VA National Rate” category or as “Number of Cases too Small.”

These categories show how hospitals' rates compare to the VA National rate 
Lower Than VA National Rate 
VA Hospitals in the “Lower Than VA National Rate” category have 30day riskadjusted rates that are lower than the VA National rate, and we can be 95% certain that this difference is not due to chance.

Within the VA National Rate 
Many hospitals in the “Within the VA National Rate” category have 30day riskadjusted rates that are about the same as the VA National rate. Other hospitals in this category have rates that are higher or lower than the VA National rate, but we cannot be 95% certain that these differences are not due to chance.

Higher Than VA National Rate 
VA hospitals in the “Higher Than VA National Rate” category have 30day riskadjusted rates that are higher than the VA National rate, and we can be 95% certain that this difference is not due to chance.

Number of Cases Too Small 
In VA hospitals that have very few eligible patients (fewer than 25 over the 3year period), the number of cases is too small (fewer than 25) to reliably tell how well the hospital is performing, so "Not Enough Cases" is displayed. 
Interval estimate 
Shows you the range of uncertainty associated with the estimated facility rate. If the National rate you are comparing falls within the interval estimate for a facility, we cannot conclude with any certainty that the two rates are really different. For example, if the interval estimate for the heart failure readmission rate for Facility A is (10%  20%) and the VA National Rate is 15%, then we cannot conclude that the readmission rate for Facility A is any different than the VA National Rate with any confidence. 