Accuracy

К оглавлению
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 
34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 
51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 
68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 
85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 
102 103 104 105 106 107 108 109 110 111 112 113 114 115 

Accuracy of measurement is an essential criterion for a data source to

be useful for understanding firearms and violence. Two key features of

accuracy are the validity and reliability of measurement. In general terms, a

measure is valid to the degree that it represents the underlying phenomenon

of interest, and it is reliable to the degree that it yields the same data over

repeated applications. Many of the debates over the relationship between

firearms and violence center on questions of validity and reliability. For

example, some analysts question the validity of the NCVS for measuring

the prevalence of defensive firearms use because, as a survey of crime

victims, the NCVS may not fully capture crimes that are averted by the use

of firearms. Other researchers question the reliability of one-time sample

surveys for measuring rare events, such as defensive use of guns. The chief

function of data standardization is to ensure reliability of measurement.

The more comprehensive a system, the more likely it will yield valid measurements

of the connection between firearms and violence.

Response errors are a vital component of the validity of any data. The

validity of data that measure firearms ownership, use, and violence on the

basis of respondent self-reports depends on the ability and willingness of

persons to disclose highly personal and sometimes incriminating or traumatic

information to interviewers. As discussed above, there are reasons to

expect response errors in regard to questions about ownership and use, as

elicited in the GSS and other gun use surveys. Although there is much

speculation on the extent and nature of response errors (see Chapter 5),

there is almost no relevant research. Likewise, validity is compromised by

nonresponse rates ranging from 20 percent (in the GSS) to over 50 percent

in some of the phone surveys used to measure ownership. Without making

unsubstantiated assumptions about gun ownership among nonrespondents,

the GSS data cannot reveal whether ownership is increasing or decreasing

over time.