Measured values of f′(x) (each accurate within ±0.2) are shown.
x
1.0
1.5
2.0
f′(x)
4.1
3.9
4.3
Based on these data and the stated measurement error, decide whether the concavity of f on the interval 1<x<2 is guaranteed to be concave up, concave down, or cannot be determined. State your conclusion and justify it briefly.