WASHINGTON (AP) — Orders for big-ticket manufactured goods dipped slightly in September as a key category that tracks business investment fell by the largest amount in seven months. U.S. manufacturing has struggled this year as American companies have been confronted by a strong dollar which makes U.S. exports more expensive in foreign markets and by the lingering effects from a big drop in oil prices which triggered big investment cutbacks at energy companies. The government will release its first look at overall economic activity in the July-September period on Friday and analysts are forecasting that the gross domestic product will rebound to growth around 2.5 percent to 3 percent, a big improvement from anemic GDP readings of 0.8 percent in the first quarter and 1.4 percent in the April-June period.