I'm getting the warning In cor.smooth(R) : Matrix was not positive definite, smoothing was done, but what is it in this case? Can I get away with that?
- code:
library(psych)
## note: Q11 and Q15 have reversed scales (thus, -1)
psych::alpha(PBQuest,
keys = c(1, 1, 1, 1, 1, -1, 1, 1, 1, -1, 1, 1, 1, 1, 1, 1, 1))
- output with the warning:
Reliability analysis
Call: psych::alpha(x = PBQuest, keys = c(1, 1, 1, 1, 1, -1, 1, 1, 1,
-1, 1, 1, 1, 1, 1, 1, 1))
raw_alpha std.alpha G6(smc) average_r S/N ase mean sd median_r
0.82 0.82 0.91 0.22 4.7 0.072 2.6 0.48 0.23
95% confidence boundaries
lower alpha upper
Feldt 0.64 0.82 0.93
Duhachek 0.68 0.82 0.96
Reliability if an item is dropped:
raw_alpha std.alpha G6(smc) average_r S/N var.r med.r
Q6 0.81 0.82 0.93 0.22 4.5 0.064 0.23
Q7 0.82 0.82 0.94 0.22 4.5 0.065 0.23
Q8 0.80 0.81 0.93 0.21 4.2 0.069 0.22
Q9 0.80 0.81 0.92 0.21 4.2 0.068 0.22
Q10 0.80 0.81 0.92 0.21 4.3 0.069 0.22
Q11- 0.81 0.82 0.93 0.22 4.5 0.069 0.23
Q12 0.81 0.81 0.95 0.21 4.3 0.067 0.23
Q13 0.80 0.81 0.92 0.21 4.2 0.070 0.22
Q14 0.82 0.82 0.94 0.22 4.6 0.065 0.23
Q15- 0.80 0.81 0.92 0.21 4.3 0.063 0.24
Q16 0.81 0.81 0.96 0.22 4.4 0.067 0.22
Q17 0.80 0.80 0.92 0.20 4.0 0.066 0.21
Q18 0.81 0.82 0.93 0.22 4.5 0.070 0.24
Q19 0.81 0.82 0.94 0.22 4.5 0.063 0.23
Q20 0.79 0.80 0.92 0.20 3.9 0.064 0.20
Q21 0.82 0.83 0.94 0.23 4.8 0.065 0.24
Q22 0.82 0.82 0.93 0.23 4.7 0.062 0.23
Item statistics
n raw.r std.r r.cor r.drop mean sd
Q6 14 0.50 0.46 0.46 0.39 2.8 1.05
Q7 14 0.42 0.42 0.41 0.30 1.9 1.07
Q8 14 0.59 0.58 0.58 0.53 3.8 0.80
Q9 14 0.65 0.62 0.61 0.55 3.1 1.23
Q10 14 0.59 0.56 0.56 0.50 3.5 1.02
Q11- 14 0.43 0.43 0.40 0.33 3.1 0.95
Q12 14 0.53 0.57 0.57 0.47 1.4 0.65
Q13 14 0.59 0.60 0.58 0.50 2.1 1.03
Q14 14 0.36 0.37 0.37 0.28 3.6 0.74
Q15- 14 0.58 0.56 0.51 0.49 2.8 0.97
Q16 14 0.47 0.51 0.52 0.38 2.3 0.91
Q17 14 0.68 0.71 0.69 0.63 1.8 0.70
Q18 14 0.43 0.44 0.39 0.32 1.9 1.00
Q19 14 0.46 0.45 0.44 0.35 1.7 0.99
Q20 14 0.77 0.76 0.67 0.72 2.5 1.02
Q21 14 0.30 0.28 0.24 0.18 2.6 1.01
Q22 14 0.32 0.35 0.32 0.22 3.4 0.85
Non missing response frequency for each item
1 2 3 4 5 miss
Q6 0.07 0.43 0.14 0.36 0.00 0
Q7 0.43 0.36 0.07 0.14 0.00 0
Q8 0.00 0.14 0.00 0.79 0.07 0
Q9 0.14 0.14 0.21 0.43 0.07 0
Q10 0.00 0.21 0.21 0.43 0.14 0
Q11 0.00 0.50 0.14 0.36 0.00 0
Q12 0.64 0.29 0.07 0.00 0.00 0
Q13 0.29 0.43 0.14 0.14 0.00 0
Q14 0.00 0.14 0.07 0.79 0.00 0
Q15 0.00 0.36 0.07 0.57 0.00 0
Q16 0.14 0.57 0.14 0.14 0.00 0
Q17 0.36 0.50 0.14 0.00 0.00 0
Q18 0.36 0.50 0.00 0.14 0.00 0
Q19 0.57 0.21 0.14 0.07 0.00 0
Q20 0.14 0.43 0.21 0.21 0.00 0
Q21 0.07 0.50 0.14 0.29 0.00 0
Q22 0.00 0.21 0.14 0.64 0.00 0
There were 20 warnings (use warnings() to see them)
> warnings()
Mensagens de aviso:
1: In cor.smooth(r) : Matrix was not positive definite, smoothing was done
2: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
3: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
4: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
5: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
6: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
7: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
8: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
9: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
10: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
11: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
12: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
13: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
14: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
15: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
16: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
17: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
18: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
19: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
20: In cor.smooth(R) : Matrix was not positive definite, smoothing was done
- the data:
> dput(PBQuest)
structure(list(Q6 = c(2, 2, 4, 4, 2, 3, 2, 2, 2, 4, 4, 1, 4,
3), Q7 = c(2, 1, 1, 1, 1, 2, 4, 4, 2, 2, 1, 1, 2, 3), Q8 = c(4,
4, 5, 4, 2, 4, 4, 4, 4, 4, 4, 2, 4, 4), Q9 = c(3, 3, 4, 4, 2,
3, 4, 4, 1, 2, 4, 1, 5, 4), Q10 = c(3, 4, 4, 3, 2, 2, 5, 5, 2,
4, 4, 3, 4, 4), Q11 = c(4, 2, 3, 2, 4, 2, 2, 2, 4, 4, 2, 3, 4,
2), Q12 = c(2, 1, 1, 2, 2, 1, 2, 1, 1, 1, 1, 1, 1, 3), Q13 = c(2,
1, 3, 2, 2, 3, 2, 2, 1, 4, 1, 2, 1, 4), Q14 = c(4, 4, 4, 4, 2,
4, 4, 4, 4, 4, 2, 3, 4, 4), Q15 = c(4, 4, 2, 2, 4, 4, 4, 4, 4,
2, 2, 3, 4, 2), Q16 = c(2, 2, 3, 2, 2, 2, 4, 2, 2, 2, 1, 3, 1,
4), Q17 = c(2, 1, 2, 2, 2, 2, 3, 2, 1, 1, 2, 1, 1, 3), Q18 = c(4,
2, 2, 1, 2, 2, 1, 2, 1, 2, 1, 1, 2, 4), Q19 = c(2, 1, 2, 3, 1,
1, 1, 1, 1, 1, 4, 2, 1, 3), Q20 = c(2, 1, 3, 3, 2, 2, 3, 2, 1,
4, 4, 2, 2, 4), Q21 = c(4, 4, 2, 2, 1, 2, 3, 2, 2, 4, 2, 2, 4,
3), Q22 = c(4, 2, 4, 4, 4, 3, 4, 2, 4, 4, 4, 3, 2, 4)), class = "data.frame", row.names = c(NA,
-14L))
- I've seen some posts for the same error, but not for calculating Cronbach's alpha. Thanks in advance!