Consider the quadratic family
$T_a(x) = a x (1 - x)$ for
$x \in [0, 1]$ and mixing Collet–Eckmann (CE) parameters
$a \in (2,4)$. For bounded
$\varphi $, set
$\tilde \varphi _{a} := \varphi - \int \varphi \, d\mu _a$, with
$\mu _a$ the unique acim of
$T_a$, and put
$(\sigma _a (\varphi ))^2 := \int \tilde \varphi _{a}^2 \, d\mu _a + 2 \sum _{i>0} \int \tilde \varphi _{a} (\tilde \varphi _{a} \circ T^i_{a}) \, d\mu _a$. For any mixing Misiurewicz parameter
$a_{*}$, we find a positive measure set
$\Omega _{*}$ of mixing CE parameters, containing
$a_{*}$ as a Lebesgue density point, such that for any Hölder
$\varphi $ with
$\sigma _{a_{*}}(\varphi )\ne 0$, there exists
$\epsilon _\varphi>0$ such that, for normalized Lebesgue measure on
$\Omega _{*}\cap [a_{*}-\epsilon _\varphi , a_{*}+\epsilon _\varphi ]$, the functions
$\xi _i(a)=\tilde \varphi _a(T_a^{i+1}(1/2))/\sigma _a (\varphi )$ satisfy an almost sure invariance principle (ASIP) for any error exponent
$\gamma>2/5$. (In particular, the Birkhoff sums satisfy this ASIP.) Our argument goes along the lines of Schnellmann’s proof for piecewise expanding maps. We need to introduce a variant of Benedicks–Carleson parameter exclusion and to exploit fractional response and uniform exponential decay of correlations from Baladi et al [Whitney–Hölder continuity of the SRB measure for transversal families of smooth unimodal maps. Invent. Math. 201 (2015), 773–844].