Retinitis pigmentosa (RP) is a hereditary ocular disease in which patches of pigment appear on the retina, potentially resulting in substantial vision loss and in some cases complete blindness. An important issue is how fast the subjects decline. Visual field is an important measure of area of vision, which is measured in degree2. A visual field area for a normal person is around 11,000 degree2. The longitudinal data in Table 11.29 were provided by an individual patient. Table 11.29 Longitudinal visual field data for one RP patient Time Visual field area ln Visit (yr) (degree2) (visual field area) 1 0 3059 8.03 2 1 3053 8.02 3 2 1418 7.26 4 3 1692 7.43 5 4 1978 7.59 6 5 1567 7.36 7 6 1919 7.56 8 7 1998 7.60 9 11 1648 7.41 10 13 1721 7.45 11 15 1264 7.14 mean 6.09 1938 7.532 sd 4.97 597 0.280 Suppose the rate of change of ln (visual field) is a linear function of follow-up time. 11.103 Write down a linear regression model that summarizes this relationship. 11.104 Fit the regression line using the method of least squares, and assess whether there is a significant change in visual field over time for this subject. Report a two-sided p-value. 11.105 What does the intercept mean in this context? What is the estimated % decline in visual field per year?
Retinitis pigmentosa (RP) is a hereditary ocular disease
in which patches of pigment appear on the retina, potentially resulting in substantial vision loss and in some
cases complete blindness. An important issue is how fast
the subjects decline. Visual field is an important measure
of area of vision, which is measured in degree2. A visual
field area for a normal person is around 11,000 degree2.
The longitudinal data in Table 11.29 were provided by an
individual patient.
Table 11.29 Longitudinal visual field data for
one RP patient
Time Visual field area ln
Visit (yr) (degree2) (visual field area)
1 0 3059 8.03
2 1 3053 8.02
3 2 1418 7.26
4 3 1692 7.43
5 4 1978 7.59
6 5 1567 7.36
7 6 1919 7.56
8 7 1998 7.60
9 11 1648 7.41
10 13 1721 7.45
11 15 1264 7.14
mean 6.09 1938 7.532
sd 4.97 597 0.280
Suppose the rate of change of ln (visual field) is a linear
function of follow-up time.
11.103 Write down a linear regression model that summarizes this relationship.
11.104 Fit the regression line using the method of least
squares, and assess whether there is a significant change
in visual field over time for this subject. Report a two-sided
p-value.
11.105 What does the intercept mean in this context?
What is the estimated % decline in visual field per year?
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