The gray-haired lady can't wait to leave the building to search for her dad. Unless watched, she will walk in the streets in an effort to find her father, who died 30 years ago.

    Not all cases of Alzheimer's disease look like this, but Alzheimer's is a serious disease that is said to be the fourth or fifth leading cause of death for people over age 75. It is said that about three percent of the U.S. population over age 65 have Alzheimer's. In the early stages; people may exhibit short-term memory loss. Some may experience changes in personality, easy to be angry. As the disease progresses, patients might lose the ability to move and may be unable to speak or move at all. This progressive disease generally lasts 8 to 10 years before death occurs.

    While no one is certain what causes these changes in the brain's nerve fibers, their effect is certain. Alzheimer's destroys not only the patients, but also spouses（配偶）, friends and families.

    What should you do if you notice progressive memory loss in yourself or a loved one? Have the person examined by a doctor who is a specialist in the treatment of Alzheimer's disease. Though many reasons other than Alzheimer's disease may cause memory loss, its early diagnosis（诊断）and treatment may delay some of the most serious effects.

    What feeling will you likely experience if a loved one suffers from Alzheimer's disease? A person will often go through the various stages of sadness, shock, anger, and so on. If the spouse develops the disease, you may experience hurt and disappointment when he or she doesn't remember you are married.

    Life for the Alzheimer's patients and their loved ones will never be the same as the disease progresses, bringing a deep sorrow, loss and even anger towards God. No matter what feelings are present, facing them honestly will serve one better than burying them.

已知一组数据1， ，3，2，4，它的平均数是3，这组数据的方差是____.

【查阅资料】