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INDEPENDENT SAMPLES T-TEST

This example is based on:

Shankweiler, D., Lundquist, E., Dreyer, L. G., & Dickinson, C. C. (1996). Reading and spelling difficulties in high school students: Causes and consequences. Reading and Writing: An Interdisciplinary Journal, 8, 267-294.


The basic skills in reading, spelling, and metalinguistic abilities were measured among high school students in the 9th and 10th grade in two school settings. One group of students attended a private school for students with learning disabilities (n=30). The other group of students contained low to average achievers who attended the public high school (n=35).

1. Decoding Skills Test, which contains two parts:

a. real words (DSTR)
b. nonwords (DSTN).

2. The second measure of reading skill, Controlled Words Decoding Test, had three components:

a. regular (CWR),
b. irregular (CWI)
c. total (CWT).

3. The final skill, Metalinguistic ability was assessed with two tasks:

a. Phoneme Deletion (PD)
b. Morphological Awareness (MORPH).

Comparisons of the mean scores of students in each setting were conducted for each skill. The following table lists the means that were compared in the study.

 

 

  Learning Disabled (n=30) Average (n=35)

 

M
SD
M
SD
Spelling
SPEL
36.51
13.19
47.70
9.4
MST
11.09
5.48
14.73
3.79
         
Reading        
DSTR
57.40
3.94
59.17
1.29
DSTN
45.69
11.37
51.40
6.20
CWR
36.80
2.60
37.77
1.45
CWI
30.60
4.24
33.77
2.70
CWT
67.40
5.85
71.53
3.79
         
Metalinguist        
PD
27.29
5.22
31.37
4.69
MORPH
77.00
5.27
79.63
2.67

Using the data presented in Shankweiler, Lundquist, Dreyer, & Dickinson's study, we will perform a power analysis.

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