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The Effects of Distance Education on K-12 Student Outcomes: A ...

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Figure 2. C<strong>on</strong>fidence intervals for individual effect sizes <str<strong>on</strong>g>of</str<strong>on</strong>g> 116 outcomes<br />

1.5<br />

1.0<br />

0.5<br />

0.0<br />

-0.5<br />

-1.0<br />

-1.5<br />

-2.0<br />

C<strong>on</strong>fidence Intervals for Individual Effect Sizes<br />

Of the 45 factors coded in the study, the following 30 were examined to determine sources <str<strong>on</strong>g>of</str<strong>on</strong>g><br />

significant variati<strong>on</strong> in effect sizes. Ten <str<strong>on</strong>g>of</str<strong>on</strong>g> the remaining variables were used for identifying the<br />

studies or computing effect size, and the other five could not be compared because the studies<br />

did not include the data for coding the variables, or the variable was not a relevant factor in the<br />

studies. <str<strong>on</strong>g>The</str<strong>on</strong>g> variables that went uncoded due to the absence <str<strong>on</strong>g>of</str<strong>on</strong>g> data were the frequency <str<strong>on</strong>g>of</str<strong>on</strong>g><br />

student participati<strong>on</strong> in distance learning, the level <str<strong>on</strong>g>of</str<strong>on</strong>g> preparati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> the teachers in distance<br />

educati<strong>on</strong>, and the amount <str<strong>on</strong>g>of</str<strong>on</strong>g> experience <str<strong>on</strong>g>of</str<strong>on</strong>g> the teachers in distance educati<strong>on</strong>. <str<strong>on</strong>g>The</str<strong>on</strong>g> variables that<br />

were not relevant factors for the studies were c<strong>on</strong>trol for the effects <str<strong>on</strong>g>of</str<strong>on</strong>g> a sec<strong>on</strong>d testing, and<br />

c<strong>on</strong>trol for the effects <str<strong>on</strong>g>of</str<strong>on</strong>g> a pretest. Analysis <str<strong>on</strong>g>of</str<strong>on</strong>g> variance was not meaningful for some <str<strong>on</strong>g>of</str<strong>on</strong>g> the<br />

variables because <str<strong>on</strong>g>of</str<strong>on</strong>g> missing data in the studies, resulting in a high number <str<strong>on</strong>g>of</str<strong>on</strong>g> cases in which a<br />

value <str<strong>on</strong>g>of</str<strong>on</strong>g> “unspecified” was coded for the variable.<br />

Publicati<strong>on</strong> and Methodological Variables<br />

Twenty variables were coded to discover whether publicati<strong>on</strong> or methodological variables<br />

accounted for variati<strong>on</strong> in effect sizes. <str<strong>on</strong>g>The</str<strong>on</strong>g> publicati<strong>on</strong> features included the year <str<strong>on</strong>g>of</str<strong>on</strong>g> publicati<strong>on</strong>,<br />

the type <str<strong>on</strong>g>of</str<strong>on</strong>g> publicati<strong>on</strong>, and the regi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> publicati<strong>on</strong>. <str<strong>on</strong>g>The</str<strong>on</strong>g> methodological variables related to the<br />

testing sequence in the study, the type <str<strong>on</strong>g>of</str<strong>on</strong>g> achievement measure used in achievement studies,<br />

pretest equivalency measures, study design, statistical power, and c<strong>on</strong>trol for <strong>12</strong> potential sources<br />

14 <str<strong>on</strong>g>of</str<strong>on</strong>g> 32

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