Answer: No, the 7:1 ratio is close to the expected 6:2 ratio even with the limited sample size.
Explanation:
Let the alleles be P (purple) and W (white).
The possible crosses are
PP x WW, PP x PW, PW x WW, PW x PW
the F1 is PP or PW
one F2 is white so the F1 must be PW and
the F2 are PP, WW, PW and
the expected 8 progeny are 2PP, 2WW, 4PW
Because 7/8 are purple, we can infer that P is dominant and W recessive, so the expectation is 6 purple, 2 white
The observed ratio is similar to the expected ratio, so we can’t say that this result disproves Mendel, particularly with a small sample.