Types of Missing Data
Missing data can occur because of nonresponse: no information is provided for several items or no information is provided for a whole unit. Some items are more sensitive for nonresponse than others, for example items about private subjects such as income.
Dropout is a type of missingness that occurs mostly when studying development over time. In this type of study the measurement is repeated after a certain period of time. Missingness occurs when participants drop out before the test ends and one or more measurements are missing.
Sometimes missing values are caused by the researchers themselves. If data collection was not done properly or if mistakes were made with the data entry (Ader, H.J., Mellenbergh, G.J. 2008).
And a great deal of missing data arise in cross-national research in economics, sociology, and political science because governments choose not to, or fail to, report critical statistics for one or more years (Messner 1992).
It is important to question why the data is missing, this can help with finding a solution to the problem. If the values are missing at random there is still information about each variable in each unit but if the values are missing systematically the problem is more severe because the sample cannot be representative of the population. For example: a research is done about the relation between IQ and income. If participants with an over average IQ do not answer the question ‘What is your salary?’ the results of the research may show that there is no association between IQ and salary, while in fact there is a relationship. Because of these problems, methodologists routinely advise researchers to design research so as to minimize the incidence of missing values (Ader, H.J., Mellenbergh, G.J. 2008).
Read more about this topic: Missing Data
Famous quotes containing the words types of, types, missing and/or data:
“The wider the range of possibilities we offer children, the more intense will be their motivations and the richer their experiences. We must widen the range of topics and goals, the types of situations we offer and their degree of structure, the kinds and combinations of resources and materials, and the possible interactions with things, peers, and adults.”
—Loris Malaguzzi (1920–1994)
“The American man is a very simple and cheap mechanism. The American woman I find a complicated and expensive one. Contrasts of feminine types are possible. I am not absolutely sure that there is more than one American man.”
—Henry Brooks Adams (1838–1918)
“In Vietnam, some of us lost control of our lives. I want my life back. I almost feel like I’ve been missing in action for twenty-two years.”
—Wanda Sparks, U.S. nurse. As quoted in the New York Times Magazine, p. 72 (November 7, 1993)
“Mental health data from the 1950’s on middle-aged women showed them to be a particularly distressed group, vulnerable to depression and feelings of uselessness. This isn’t surprising. If society tells you that your main role is to be attractive to men and you are getting crow’s feet, and to be a mother to children and yours are leaving home, no wonder you are distressed.”
—Grace Baruch (20th century)